EasyJet has begun a legal challenge against the merger between Air France and KLM on the grounds it would substantially reduce consumer choice.
Europe's second-largest no-frills carrier said on Tuesday it had submitted an appeal to the Court of First Instance in Luxembourg, requesting it to annul the European Commission's clearance of the Air France-KLM merger.
"It is clear that, in its current form, the Air France and KLM merger strengthens the dominant position of Air France and would set a worrying precedent for all future consolidation," Chief Executive Ray Webster said.
The British carrier has already bitterly complained about the allocation of take-off and landing slots at French airports, particularly Air France's dominance at Paris Orly airport.
EasyJet said last week it planned to file a complaint in a French court against Cohor, the agency that assigns slots at French airports, alleging it was too close to Air France.
The European Commission, the executive arm of the European Union, had failed to consider the impact of Air France-KLM merger on the "impregnable dominance" of the two airlines at their respective hubs in Paris and Amsterdam, easyJet said.
Brussels cleared the Air France-KLM merger in February.