Exclusion of Terminal Capacity Planning Conditions as Article 6 Constraints in EU Slot Regulation Coordination Parameters

Introduction

Aer Lingus Ltd & Ors v Irish Aviation Authority ([2025] IEHC 190) is a High Court judicial review concerning the Irish Aviation Authority’s (IAA) biannual setting of slot coordination parameters at Dublin Airport under Council Regulation (EEC) No 95/93. The key issue is whether two planning conditions—limiting combined terminal capacity to 32 million passengers per annum (“32mppa conditions”)—are “relevant technical, operational and environmental constraints” that the IAA must lawfully take into account under Article 6 of the Slot Regulation. Airlines (Aer Lingus, Ryanair, A4A carriers) contend that the 32mppa conditions cannot qualify as constraints under Article 6; the IAA and daa (Dublin Airport Authority) disagree. The court was asked for an injunction preventing the IAA from factoring in the contested conditions when setting upcoming Winter 2025 coordination parameters, pending the substantive judicial review and a reference to the Court of Justice of the European Union.

Summary of the Judgment

Delivered by Mr. Justice Barry O’Donnell on 2 April 2025, the judgment grants the airline applicants’ interlocutory injunction. It restrains the IAA from taking account of the 32mppa planning conditions in determining coordination parameters for Winter 2025 (and subsequent seasons) until the main proceedings conclude. The court held:

It has jurisdiction under Order 84, rule 20 of the Rules of the Superior Courts to grant interim relief (injunction) pending judicial review.
The relief sought is prohibitory (restraining the IAA from a given course of action), not mandatory.
In applying the private-law injunction test (likelihood of success, irreparable harm, balance of convenience), the applicants demonstrated they would suffer serious, irreparable harm—loss of historic and ad hoc slots, massive revenue shortfalls—if the IAA proceeded to impose Passenger Air Traffic Movement (PATM) seat caps derived from the 32mppa conditions.
The balance of justice favors interim non-application of the 32mppa conditions—avoiding repeated seasonal challenges and protecting airlines and passengers—pending a definitive ruling on whether those conditions qualify as Article 6 constraints.

Analysis

Precedents Cited

Okunade v Minister for Justice [2012] 3 IR 152 – Criteria for judicial review injunction (likelihood of success, irreparable harm, balance of convenience).
Tormey v Ireland [1985] IR 289 – High Court’s constitutional “full original jurisdiction” and limits on stepping into statutory decision-maker’s role.
Criminal Assets Bureau v Hunt [2003] 2 IR 168 – Extension of Tormey to other tribunals with limited judicial powers.
Grianán an Aileach Company Ltd v Donegal County Council [2004] 2 IR 625 – High Court should not pre-empt planning authority decisions by granting overly wide declaratory relief that usurps statutory processes.
Pesca Valentia v Minister for Fisheries [1985] IR 193 – Scope for interlocutory injunction restraining statutory enforcement pending review.
PMcD v Governor of X Prison [2022] 1 IR 741 – Declaratory relief can stand alone, and often suffices without mandatory orders.
Maha Lingam v HSE [2005] IESC 89 – Higher threshold for mandatory interlocutory injunction.
Ryanair v Skyscanner [2022] IECA 64 – Substance of injunction determines whether it is prohibitory or mandatory.

Legal Reasoning

The court’s reasoning proceeded in three stages:

Jurisdiction: Under Order 84, rule 20(8) RSC, the court may grant stays or injunctions ancillary to judicial review. It confirmed that an injunction restraining future conduct (prohibitory) is available and governed by the private-law injunction principles.
Nature of Relief—Prohibitory vs Mandatory: The injunction sought simply prevents the IAA from considering the 32mppa conditions; it does not command the IAA to take any specific positive action. Therefore it is prohibitory, requiring the lower threshold test on the balance of convenience.
Balance of Convenience & Irreparable Harm:
- Irreparable harm: Evidence showed significant losses—lost historic slots (often irrecoverable), pool slots, and tens of millions of euros in revenue—should seasonal seat caps be imposed.
- Likelihood of success: Major legal dispute as to whether planning conditions qualify under Article 6; strong arguable case exists.
- Balance of justice: The court must prevent serious harm to airlines and avoid wasteful, repetitive litigation each season; regulatory certainty benefits all stakeholders.

The court refused daa’s proposed amendment to limit the injunction to preserving historic slots because: (a) it would amount to a quasi-mandatory order directing slot-allocation outcomes beyond mere parameter-setting; (b) it conflicted with the Slot Regulation scheme (the IAA sets parameters, Aircraft Coordination Limited allocates specific slots); and (c) the IAA itself opposed that formulation as unworkable.

Impact

On Irish Slot Coordination: Pending final resolution, the IAA must omit the 32mppa restrictions from its forthcoming Winter 2025 and Summer 2026 coordination parameter decisions. Airlines will be able to maintain existing service levels, protect historic and ad hoc slots, and avoid repeated urgent litigation.

On Planning–Regulation Interface: The ruling highlights the legal boundary between land-use planning conditions (planning authorities) and operational constraints under EU slot regulation. It suggests that not all planning-imposed limits automatically qualify as “technical, operational or environmental constraints” under Article 6.

On Interim Relief in Ongoing Administrative Processes: Confirms that Irish courts may grant prohibitory injunctions against public bodies in the midst of statutory decision-making processes where contested legal issues and potential irreparable harm justify early intervention.

Complex Concepts Simplified

Council Regulation 95/93 (Slot Regulation): EU law requiring coordinated allocation of take-off and landing slots at busy Community airports when demand exceeds capacity.
Article 6 Constraints: The IAA must consider “all relevant technical, operational and environmental constraints” (e.g., runway capacity, noise limits) when setting coordination parameters.
Coordination Parameters: Biannual caps on flights or seats (known as Passenger Air Traffic Movement or PATM seat caps) to ensure orderly slot allocation.
32mppa Planning Conditions: Conditions imposed by An Bord Pleanála limiting combined annual passenger throughput at Dublin's Terminals 1 & 2 to 32 million, unless further planning permission is granted.
Interlocutory Injunction vs Stay:
- A stay suspends the legal effect of an already-made decision pending review.
- An interlocutory injunction forbids a public body from taking certain steps in the future (here, factoring in the 32mppa conditions), pending final determination.
Balance of Convenience Test: Courts weigh the risk of irreparable harm against potential prejudice to the public body; if the harm to the applicant outweighs the risk of injustice to the respondent, relief may be granted.

Conclusion

The High Court’s decision in Aer Lingus Ltd & Ors v Irish Aviation Authority establishes that, pending the outcome of substantive judicial review and a CJEU reference, the IAA must exclude terminal capacity planning conditions from its Article 6 constraint analysis when setting slot coordination parameters. By granting an interlocutory injunction, the court prevented immediate harm to airlines and airport users and underscored the judiciary’s role in safeguarding statutory decision-making from contested legal interpretations. The ruling will shape future slot-allocation processes and clarifies the interplay between planning conditions and EU aviation regulation.