Reducing airport capacity on climate grounds under the EU Slot Regulation

Our new expert legal opinion dispels myths about the EU’s Slot Regulation. We find that climate laws that set environmental airport caps can be used to reduce airport slots and airlines do not have property rights in slots.  

Background 

The EU Slot Regulation provides Member States with general rules on airport slot allocation and reduction. Opportunity Green commissioned a legal opinion from Tiffany Tang of Fountain Court Chambers to clarify whether slot coordinators can limit airport capacity in line with climate laws and whether airlines hold property rights in their “historic slots”. The findings confirm that coordinators can lawfully reduce slot capacity on climate grounds where there is a binding legal obligation to reduce airport capacity for environmental reasons.

At the time of writing, the European Commission is conducting a “fitness check” of EU airport legislation, including the Slot Regulation, to assess effectiveness and coherence with broader policies such as the EU Green Deal and international law (consultation closing on 28 October 2025). This review provides a critical opportunity to align the EU’s aviation laws with its climate objectives, the EU Green Deal, and international legal obligations to reduce aviation emissions.

What’s in the briefing?  

The independent legal opinion finds:

• Climate laws that legally require reduced airport capacity qualify as “environmental constraints” that slot coordinators should take account of when allocating slots. Slot coordinators can therefore reduce slots under current rules when capacity limits are legally required for climate reasons.

• Broader climate-related measures, such as national carbon budgets, may also count as environmental constraints if they affect airport infrastructure.

• Air carriers do not have a proprietary right to “historic slots” – the allocation of such slots remains conditional and at the coordinator’s discretion.