Starting from April 2022, the French Government has decided to try to reduce pollution from airlines by banning short haul flights within France ( flights of under 2½ hours), on the basis that there is an efficient network of high speed trains which offers a suitable alternative.
Whilst flight times will often be shorter by air, times from city centre to city centre are often as quick by rail, avoiding security and other airport procedures, plus the time spent getting from the airport to city centre or vice versa. It will all depend on individual journeys.
see www.bbc.co.uk