Although the move was included in a 2021 climate law and already applied in practice, some airlines had asked the European Commission to investigate whether it was legal.
The change mostly rules out air trips between Paris and regional hubs such as Nantes, Lyon and Bordeaux, with connecting flights unaffected.
Critics have noted that the cutoff point for comparable train journeys is shy of the roughly three hours it takes to travel from Paris to Mediterranean port city Marseille by high-speed rail.
The original proposal – put forward by the citizens’ convention on the climate – was to ban any flight for journeys that could be done within six hours by rail, but this was watered down as the bill passed through parliament.
The law also specifies that train services on the same route must be frequent, timely and well-connected enough to meet the needs of passengers who would otherwise travel by air – and able to absorb the increase in passenger numbers.
People making such trips should be able to make outbound and return train journeys on the same day, having spent eight hours at their destination.
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The law affects only commercial flights, not journeys taken by private jet. The government had already secured Air France’s compliance with the plan in exchange for a 2020 Covid financial support package.
Competitors were banned from simply filling the gap.
The step comes as French politicians have also been debating how to reduce emissions from private jets.
While Green MPs have called for banning small private flights altogether, Transport Minister Clement Beaune last month trailed a higher climate charge for users from next year.
The French football team Paris-Saint-Germain last year came in for an avalanche of criticism for travelling by plane to a match in Nantes – a journey that could be made by train in just two hours.