Is it totally necessary to book train seats online prior to departure? We want to take train to Caen on Sat,5/14 & return on Tuesday, 5/17. I'm confused by what they call "Flexible Tickets". If we confirm seats & for some reason we miss the train, can we just use them towards the next train departing? Or do I have to add the flexible part at same time as booking? If we just show up & try for next available train, is there possibility we won't get on at all? Thank you.
With a "flexible fare", you can exchange it free of charge BEFORE scheduled departure. After departure, you can get 50% back. So it is not like you can show up late and jump on another train.
Or you can not book and just show up and buy a full fare ticket for the next train.
You might be better off with the OuiBus which goes from La Defense and only takes 2 hours and 50 minutes and costs 9 euro.
Trains on this line don't require seat assignments, therefore they never block you from boarding if you have a valid ticket or rail pass.