Civil Law and Aviation Weather Prediction System Failure Disputes in Europe

1. Introduction

An aviation weather prediction system failure occurs when an airline, airport, air-navigation provider, meteorological service, or technology supplier relies on a weather-information system that gives incorrect, incomplete, delayed, unavailable, or corrupted weather information, and that failure contributes to:

flight cancellation;

flight delay;

diversion;

unsafe routing;

missed connections;

airport closure decisions;

additional fuel consumption;

passenger accommodation expenses;

aircraft damage;

operational losses; or

passenger compensation claims.

European law does not yet have a single, dedicated statutory regime called "weather prediction system failure liability." Instead, the legal problem is divided among Regulation 261/2004, air-navigation law, contract law, negligence/delict, the Montreal Convention, product/software liability, and national civil law.

A particularly important development is the 2026 CJEU judgment in Republik Österreich v Austrian Airlines, C-408/24, which concerns failure of an aeronautical telecommunications system and the financial losses suffered by an airline. Although it is not a weather-forecast case, it is highly relevant by analogy to failures of safety-critical aviation information infrastructure. (Eur-Lex)

2. What Is a Weather Prediction System?

An aviation weather prediction system can include:

meteorological satellites;

radar systems;

airport weather stations;

wind-shear detection systems;

numerical weather prediction models;

turbulence prediction systems;

icing forecasts;

visibility and fog forecasts;

lightning detection;

volcanic-weather monitoring;

aviation meteorological databases;

automated weather observation systems;

weather-data APIs;

aircraft weather radar;

AI-based forecasting systems; and

communications systems transmitting forecasts to pilots and air-traffic services.

A failure may therefore occur at several different levels.

Example

A weather service predicts:

visibility 5 km, wind 8 knots.

The actual conditions shortly afterward are:

visibility 400 metres, severe crosswinds and wind shear.

The airline operates based on the forecast, the airport becomes unusable, and flights are cancelled.

The resulting legal question is:

Who bears the loss?

Possible defendants include:

meteorological service;

software developer;

cloud-service provider;

airport operator;

air-navigation service provider;

airline;

aircraft manufacturer;

data supplier; or

public authority.

3. Main European Legal Framework

A. Regulation 261/2004

For passenger claims, Regulation 261/2004 is normally the starting point.

It covers:

cancellation;

long delay;

denied boarding;

assistance;

rerouting;

reimbursement; and

fixed compensation.

Article 5(3) provides an exemption from fixed compensation where the carrier proves that cancellation or delay resulted from extraordinary circumstances that could not have been avoided even if all reasonable measures had been taken.

Importantly, the Regulation itself identifies meteorological conditions incompatible with the operation of the flight as an example of circumstances that may produce extraordinary circumstances. But the CJEU has repeatedly held that the mere presence of weather conditions does not automatically establish the exemption. (Infocuria)

4. Bifurcation of the Legal Problem

A weather-system dispute should be divided into two questions.

Question 1 — Passenger versus airline

Example:

Weather prediction system fails → flight cancelled → passenger claims compensation from airline.

The main issue is Regulation 261/2004.

Question 2 — Airline versus weather-system provider

Example:

Weather prediction system fails → airline cancels 40 flights → airline suffers €5 million loss.

This is a different civil-liability dispute involving:

contract;

negligence;

statutory duties;

air-navigation legislation;

causation;

limitation of liability;

professional standards; and

potentially public-authority liability.

The recent Austrian Airlines judgment is especially significant for this second category. (Eur-Lex)

5. Case Law 1 — Wallentin-Hermann v Alitalia

CJEU, Case C-549/07, 22 December 2008

This is one of the foundational cases.

Facts

A flight was cancelled because of a technical problem.

The airline argued that the technical problem constituted an extraordinary circumstance.

Decision

The CJEU established the basic test:

An event is extraordinary only if, by its nature or origin:

it is not inherent in the normal exercise of the carrier's activity; and

it is beyond the carrier's actual control.

The Court also emphasized that the examples in recital 14, including meteorological conditions, are not automatically extraordinary in every case. (Infocuria)

Relevance to weather prediction failure

Suppose an airline says:

"The weather was bad, therefore we owe no compensation."

That is insufficient by itself.

The court can ask:

What exactly happened?

Was the weather genuinely incompatible with safe operation?

Was the airline warned sufficiently early?

Did the airline have accurate information?

Did it take reasonable measures?

Did the system failure contribute to the cancellation?

Principle

Bad weather and weather-information failure must be separately analysed.

6. Case Law 2 — Eglītis and Ratnieks v Latvijas Republikas Ekonomikas ministrija

CJEU, Case C-294/10, 12 May 2011

Issue

The case concerned the airline's obligation to take reasonable measures following extraordinary circumstances.

Decision

The CJEU emphasized that an airline cannot simply wait for an extraordinary event to disappear and then claim exemption.

It must organize its resources so that operations can resume as soon as reasonably possible. (Infocuria)

Application to weather prediction systems

Assume a forecasting system fails for six hours.

The airline may need to consider:

alternative weather data;

other meteorological sources;

manual weather observations;

alternative aircraft;

alternative routes;

different departure times;

airport alternatives;

crew arrangements.

The failure of one forecasting system does not necessarily justify indefinite disruption.

Principle

Reasonable operational mitigation remains relevant even when the original weather event is extraordinary.

7. Case Law 3 — McDonagh v Ryanair

CJEU, Case C-12/11, 31 January 2013

Facts

The eruption of the Icelandic volcano Eyjafjallajökull caused extensive European airspace restrictions.

Passengers were stranded.

Decision

The volcanic eruption constituted an extraordinary circumstance for Regulation 261/2004 purposes.

However, the airline's duty to provide care did not disappear.

Passengers could still be entitled to:

meals;

refreshments;

accommodation;

communication facilities; and

other appropriate care.

Relevance

This case demonstrates an important distinction:

No fixed compensation does not necessarily mean no passenger rights.

A weather-system failure may similarly result in a situation where the airline can invoke an extraordinary circumstance for fixed compensation but still owes passengers statutory care and assistance.

8. Case Law 4 — Pešková and Peška v Travel Service

CJEU, Case C-315/15, 4 May 2017

Facts

An aircraft suffered a bird strike, which caused disruption.

Decision

The CJEU accepted that a bird strike can constitute an extraordinary circumstance.

But the carrier must still demonstrate that reasonable measures were taken to prevent or reduce the consequences.

Relevance to weather systems

The analogy is important.

Suppose:

Weather prediction system gives incorrect information.

The carrier or system provider may argue that the underlying weather event was outside its control.

But a court can separately examine:

backup weather systems;

redundancy;

manual verification;

alternative forecasts;

warnings;

technical maintenance;

data validation;

contingency procedures.

Principle

An external natural event and the failure to manage its consequences are separate questions.

9. Case Law 5 — Siewert and Others v Condor Flugdienst

CJEU, Case C-394/14, 17 September 2015

This case concerned the interpretation of extraordinary circumstances in relation to an external event affecting an aircraft.

The CJEU's jurisprudence distinguishes between events that are truly external to the carrier and events arising from the normal operation of the carrier's own equipment and systems.

The broader principle is relevant to weather technology:

External event

Example:

Unexpected severe storm makes runway unusable.

Internal system failure

Example:

Airline's own weather-processing software incorrectly interprets available meteorological data.

These should not automatically receive identical legal treatment.

10. Case Law 6 — Krüsemann and Others v TUIfly

CJEU, Joined Cases C-195/17 and Others, 17 April 2018

Principle

The CJEU emphasized that even events mentioned in recital 14 of Regulation 261/2004 must be examined according to their actual characteristics.

The extraordinary-circumstances exception is not automatic. (Infocuria)

Application

For weather-prediction disputes, the court can distinguish:

A. Genuine severe weather

from

B. Failure to interpret available weather information

from

C. Failure of the airline's forecasting software

from

D. Failure of an external meteorological provider

from

E. Failure of an air-navigation authority's weather-information infrastructure.

Each can generate different liability questions.

11. Case Law 7 — D (Air Traffic Management Decision)

General Court, Case T-134/25, 21 January 2026

This is particularly relevant to the present topic.

Facts

The case concerned passenger compensation following an air-traffic-management decision associated with adverse weather conditions.

The decision involved allocation of delayed departure slots following adverse weather.

Decision

The General Court considered an air-traffic-management decision to be external to the ordinary activity of an airline where the carrier did not contribute to that decision.

It therefore considered such a decision capable of constituting an extraordinary circumstance under Article 5(3). (Infocuria)

Important qualification

The case is currently subject to review by the CJEU in Case C-108/26 RX, following a decision of 12 March 2026. The review concerns whether the General Court's judgment affects the unity or consistency of EU law. Therefore, the January 2026 General Court reasoning should not be treated as the final word on the issue. (Curia)

Importance

This is highly relevant where:

weather prediction → air-traffic-management restriction → flight delay/cancellation.

It shows the importance of separating:

weather event → meteorological information → air-traffic-management decision → airline operational response.

12. Case Law 8 — Republik Österreich v Austrian Airlines

CJEU, Case C-408/24, judgment 12 February 2026

This is perhaps the most important analogical infrastructure-liability case for a weather prediction system failure.

Facts

A failure of an aeronautical telecommunications server operated by the air-navigation service provider caused a substantial reduction in take-off and landing capacity at Vienna Airport.

Austrian Airlines had to cancel 60 flights.

It claimed approximately €373,000 in losses, including:

ticket refunds;

rerouting;

codeshare losses;

passenger catering;

accommodation;

passenger transportation;

baggage handling; and

staff overtime.

The dispute concerned whether European air-navigation rules protect airspace users against material damage caused by culpable failure of an air-navigation service provider.

CJEU decision

The CJEU held that the relevant EU air-navigation framework is capable of protecting airspace users against material damage resulting from a culpable failure by an air-traffic service provider to comply with its obligations. (Eur-Lex)

Relevance to weather forecasting

Imagine instead:

Meteorological-data server fails → airport receives incorrect/incomplete weather information → flights are unnecessarily cancelled → airline suffers measurable financial losses.

The Austrian Airlines reasoning provides an important legal analogy for determining whether regulatory obligations concerning aviation infrastructure can have a protective function for airspace users.

Important limitation

The case did not decide liability for a weather forecasting error itself.

It concerned an aeronautical telecommunications server, so its application to meteorological systems remains analogical and depends on the applicable national and EU rules.

13. Case Law 9 — WZ v Austrian Airlines

CJEU, Case C-826/19, 22 April 2021

The case concerned a flight that was diverted to another airport serving the same city/region and the consequences under Regulation 261/2004.

The Court examined:

cancellation;

delay;

passenger assistance;

rerouting;

transportation between airports.

(curia)

Relevance

Weather prediction failure can produce a diversion rather than a cancellation.

For example:

Forecast indicates safe landing → conditions deteriorate → aircraft diverts to another airport.

The legal analysis must therefore consider not only whether compensation is payable, but also whether the airline fulfilled its obligations concerning transportation and passenger assistance.

14. Case Law 10 — Airhelp v Scandinavian Airlines System

CJEU, Case C-28/20, 23 March 2021

This case concerned a pilots' strike rather than weather.

Its importance here is doctrinal.

The CJEU emphasized that the concept of extraordinary circumstances depends on whether the event is:

external to the carrier;

outside its actual control; and

not inherent in its normal activity.

(Infocuria)

Application

The same framework helps distinguish:

External weather event

from

internal forecasting-system failure.

15. Core Legal Issue: Was the Weather Actually Unpredictable?

This is one of the most important issues.

A defendant may argue:

"The storm was unpredictable."

But a court may ask:

What forecasts existed?

When were they issued?

What did radar show?

What did satellite information show?

Were warnings available?

Did other meteorological systems predict the event?

Was the system properly maintained?

Was the failure technical or methodological?

Was the weather model appropriate?

Was the forecast probability communicated correctly?

Therefore:

"The weather was unexpected" ≠ automatically "the system was not negligent."

16. Weather Prediction Error vs Weather System Failure

These should be distinguished.

A. Prediction error

The forecasting model works correctly but predicts the wrong weather.

Example:

Model predicts 2,000-metre visibility but actual visibility falls to 500 metres.

This raises questions about:

reasonable forecasting methodology;

scientific uncertainty;

probability;

accepted professional standards.

B. Technical failure

The system stops functioning.

Example:

Meteorological server crashes for three hours.

This raises questions about:

maintenance;

redundancy;

cybersecurity;

backup systems;

service-level agreements;

negligence.

C. Data failure

The system receives incorrect data.

Example:

Wind sensor transmits 8 knots instead of 48 knots.

Potential defendants could include:

sensor manufacturer;

maintenance company;

airport;

meteorological provider.

D. Communication failure

Correct information exists but is not transmitted.

This can involve:

aviation communications;

data-link systems;

air-navigation services;

software interfaces.

17. Contractual Liability

A weather-information provider may have a contract with:

airline;

airport;

air-navigation service provider;

government;

aircraft operator.

The contract may specify:

forecast accuracy;

availability;

response times;

maintenance;

system uptime;

emergency support;

data quality;

liability caps;

exclusions;

indemnities;

force majeure.

Example

A weather-data provider guarantees:

99.9% system availability.

If the system is unavailable for a prolonged period, the airline might pursue a contractual claim.

However, the contract may limit damages to:

annual subscription fees.

Therefore, contractual limitation clauses become important.

18. Negligence / Delict

A civil claim may involve:

Duty

Did the provider owe a duty to the claimant?

Breach

Was the system operated below the applicable professional standard?

Causation

Did the system failure actually cause the loss?

Damage

Was there legally recoverable loss?

Defences

Was the event:

unforeseeable;

unavoidable;

caused by a third party;

force majeure;

outside the provider's control?

19. Causation Is Often the Hardest Issue

Suppose:

Weather forecast error → airline continues operation → airport closes → flight cancelled.

The claimant must establish the causal chain.

Possible alternative causes include:

actual severe weather;

ATC restriction;

runway closure;

airport decision;

crew limitations;

aircraft availability;

passenger-handling limitations.

A court may ask:

Would the same cancellation have occurred even if the weather forecast had been accurate?

If the answer is yes, damages attributable to the forecasting failure may be difficult to establish.

20. Concurrent Causes

A single flight disruption can have several causes:

Weather forecast error

↓

Late airline decision

↓

ATC restriction

↓

Airport closure

↓

Flight cancellation

↓

Passenger loss

The legal system may therefore have to determine:

primary cause;

contributing cause;

intervening cause;

foreseeable consequence;

remoteness of damage.

21. Airline's Own Liability to Passengers

Even where the airline's weather-data supplier is at fault, the passenger normally looks first to the operating carrier under the applicable passenger-rights regime.

The airline may subsequently seek recovery from the weather-data provider through:

contractual indemnity;

contribution;

negligence;

subrogation;

insurance;

other applicable national remedies.

Thus:

Passenger claim and supplier claim are legally separate.

22. Weather Information and Extraordinary Circumstances

A particularly important distinction is:

Situation A

A reliable forecasting system accurately predicts extreme weather.

The weather makes flight operation impossible.

→ Extraordinary-circumstances defence may potentially apply.

Situation B

The airline's own forecasting system malfunctions.

The weather itself is manageable, but the airline wrongly believes it is dangerous.

→ The airline may have difficulty treating its own system failure as an extraordinary circumstance.

Situation C

An external meteorological service fails.

The airline had no reasonable alternative source and the failure caused unavoidable disruption.

→ The facts concerning external control and reasonable measures become critical.

Situation D

The weather-data provider had a contractual duty to maintain a redundant system but failed to do so.

→ A separate contractual/negligence claim may arise.

23. Standard of Care for Aviation Weather Systems

A court may examine whether the provider used appropriate:

meteorological models;

hardware;

software;

data validation;

sensor calibration;

cybersecurity;

backup systems;

disaster recovery;

redundancy;

maintenance;

human supervision;

alert systems.

For AI-based weather prediction, additional questions can arise:

training-data quality;

model validation;

model drift;

confidence intervals;

explainability;

monitoring;

human oversight;

failure detection.

24. AI Weather Prediction Systems

Modern aviation may increasingly use AI to predict:

turbulence;

storms;

wind shear;

icing;

visibility;

precipitation;

runway conditions.

An AI forecasting failure could therefore produce a new category of civil disputes.

Example

An AI system predicts:

low turbulence risk.

Actual turbulence becomes severe and an aircraft is damaged.

Potential issues include:

defective software;

inadequate training data;

insufficient validation;

improper deployment;

inadequate human supervision;

failure to communicate uncertainty;

cybersecurity attack;

incorrect sensor data;

negligent maintenance.

The applicable product/software-liability rules must then be considered alongside aviation-specific regulation.

25. Evidence in Weather-System Litigation

Evidence can include:

Meteorological evidence

radar images;

satellite data;

METAR reports;

TAF forecasts;

SIGMETs;

NOTAMs;

wind measurements;

visibility reports;

weather warnings.

Technical evidence

server logs;

system uptime records;

error logs;

API logs;

backup records;

maintenance records;

software versions;

cybersecurity logs.

Aviation evidence

flight plans;

ATC instructions;

dispatch records;

pilot reports;

operational-control records;

diversion records.

Passenger evidence

booking records;

boarding passes;

delay notices;

hotel invoices;

meal receipts;

rerouting records.

26. Expert Evidence

Expert witnesses may include:

meteorologists;

aviation safety experts;

software engineers;

data scientists;

air-traffic-management experts;

aircraft engineers;

economists;

aviation operations specialists.

The expert's task may be to answer:

Was the forecast reasonably accurate according to professional standards?

and:

Would a properly functioning system probably have changed the operational decision?

27. Liability of Different Actors

Liability is highly dependent on national law and contractual allocation.

28. The Austrian Airlines Case and Infrastructure Liability

The 2026 Austrian Airlines judgment deserves special attention.

The CJEU found that the EU framework governing air-navigation services is capable of protecting airspace users against material damage caused by a culpable failure of an air-navigation service provider to comply with its obligations. (Eur-Lex)

This is significant because a future weather-data dispute could involve a similar infrastructure chain:

Weather sensor

→ meteorological server

→ aviation data network

→ air-navigation service

→ airline

→ passengers

The legal analysis may therefore involve several interconnected duties rather than simply asking whether the airline "made a mistake."

29. Relationship with Regulation 261/2004

A weather-system failure can create two different claims.

Claim 1 — Passenger → Airline

Possible Regulation 261/2004 compensation.

Claim 2 — Airline → Weather-system provider

Possible civil/commercial claim for:

ticket refunds;

rerouting costs;

accommodation;

catering;

aircraft repositioning;

crew costs;

lost revenue;

other proven losses.

These claims should not be confused.

30. Montreal Convention

Where a passenger seeks individual damages arising from delay, the Montreal Convention may become relevant.

This is different from the standardized compensation mechanism under Regulation 261/2004.

The CJEU has repeatedly distinguished the two regimes.

In Wallentin-Hermann, the Court emphasized that the Regulation's standardized compensation mechanism and the Montreal Convention's individual damages regime operate in different contexts. (Infocuria)

31. Force Majeure

A weather-system provider or airline may invoke force majeure.

But the precise legal effect depends upon:

contract wording;

national law;

nature of the event;

foreseeability;

avoidability;

reasonable preventive measures.

For example:

Severe hurricane

May potentially constitute force majeure.

Failure to maintain backup servers

Less obviously force majeure because the failure may be within the provider's operational control.

32. Limitation of Liability

Technology and weather-data contracts may contain:

maximum liability caps;

exclusions for consequential loss;

exclusions of lost profits;

service credits;

force-majeure clauses;

indemnity provisions.

A major issue may therefore be:

Even if the provider breached the contract, how much can the airline recover?

National mandatory law may affect the enforceability of particular exclusions.

33. Passenger Compensation Calculation

Where Regulation 261/2004 applies, fixed compensation generally follows the statutory distance categories:

The existence of a weather-system failure does not itself determine whether compensation is payable.

The court must examine the actual causal circumstances and the Article 5(3) extraordinary-circumstances requirements.

34. Important Distinction: Forecast Error vs Actual Weather

This is an excellent examination issue.

Forecast error

"The weather prediction was wrong."

This concerns the performance of an information system.

Actual weather event

"The storm made operation unsafe."

This concerns the external physical event.

Legal analysis

A court should not automatically treat these as the same event.

The chain may be:

Actual weather

Forecast quality

Information availability

Airline decision

ATC decision

Operational response

=

Legal causation

35. Practical Hypothetical

Suppose an airline operates:

Paris → Amsterdam

The airline receives a weather forecast indicating safe conditions.

The forecast system has actually failed to process an approaching severe storm.

The aircraft departs.

A severe storm develops.

The aircraft diverts.

Passengers arrive five hours late.

Passenger claim

The passenger may claim under Regulation 261/2004.

Airline defence

The airline may argue:

"The storm was extraordinary."

Passenger's response

The passenger may argue:

"The disruption resulted from a preventable forecasting-system failure."

Court's questions

Was the actual weather extraordinary?

Was the forecast system functioning correctly?

Was the weather information reasonably available?

Did the airline have alternative weather sources?

Could the airline reasonably have avoided the disruption?

Did the airline take reasonable measures?

Was the delay at the final destination at least three hours?

Did the airline provide required care?

36. Second Hypothetical — Airline v Weather Provider

Assume the weather provider contractually promised:

99.99% availability and validated aviation forecasts.

The provider's server failed for four hours.

The airline cancelled 50 flights.

Losses:

€1 million passenger refunds;

€300,000 accommodation;

€100,000 rerouting;

€200,000 crew expenses.

The airline could potentially pursue:

Contractual damages + applicable indemnity + negligence claim, subject to contractual limitations and national law.

The Austrian Airlines decision provides an important European-law analogy where failure of aviation infrastructure causes measurable economic loss to an airspace user. (Eur-Lex)

37. Six Core Legal Tests

For an aviation weather prediction system failure dispute, use these six questions:

Test 1 — What failed?

Weather event, forecast, sensor, server, software, communications or ATC?

Test 2 — Who controlled it?

Airline, airport, meteorological provider, air-navigation authority or technology supplier?

Test 3 — Was the event extraordinary?

Apply the CJEU's two-part test:

not inherent in normal airline activity;

beyond actual control.

Test 4 — Were reasonable measures taken?

Consider alternative data and operational responses.

Test 5 — Did the failure cause the loss?

Establish factual and legal causation.

Test 6 — What remedy is available?

Consider:

Regulation 261/2004;

care;

reimbursement;

rerouting;

Montreal Convention;

contract;

negligence;

statutory liability.

38. Case-Law Revision Table

39. Current 2026 Position

Two developments are especially important for this topic.

First — Austrian Airlines, C-408/24

The CJEU's 12 February 2026 judgment recognizes that the EU air-navigation framework can protect airspace users from material damage caused by culpable failure of an air-navigation service provider. (Eur-Lex)

Second — D, T-134/25

The General Court's 21 January 2026 judgment dealt specifically with an air-traffic-management decision connected with adverse weather conditions and passenger compensation. However, the judgment is under review in C-108/26 RX, so its legal position should be treated cautiously rather than as settled final CJEU law. (Infocuria)

40. Conclusion

Aviation weather prediction system failure disputes in Europe sit at the intersection of passenger-rights law, aviation regulation, civil liability, technology liability and meteorological uncertainty.

The most important distinction is:

The existence of bad weather does not automatically determine liability.

The court must examine the entire causal chain:

Weather event → Forecast → Weather-data system → Communication → Airline decision → ATC decision → Flight disruption → Passenger/economic loss.

The major legal principles are:

Meteorological conditions may constitute extraordinary circumstances, but not automatically.

The airline must establish the Article 5(3) requirements.

Reasonable measures remain important.

Duty of care can survive an extraordinary-circumstances defence.

Forecast-system failure must be distinguished from the underlying weather event.

Internal system failures and genuinely external events may receive different treatment.

Airline liability to passengers is distinct from the airline's potential claim against a weather-data provider.

Causation is critical where several factors contribute to the disruption.

The 2026 Austrian Airlines judgment is highly relevant by analogy to failures of aviation information infrastructure.

The 2026 D judgment concerning adverse-weather-related air-traffic management is particularly relevant, but remains subject to CJEU review.

Exam formula

Weather Prediction Failure Liability =

Weather Event + Forecast Accuracy + System Reliability + External/Internal Control + Extraordinary Circumstances + Reasonable Measures + Causation + Operating Carrier Liability + Infrastructure/Provider Liability + Regulation 261/2004 + Montreal Convention + Contract/Negligence + Damages.