And you can find round trip tickets Madrid-Paris on RyanAir for 50 eur, and for 100 eur on regular airlines. In my comment I took 140 eur as typical price of airfare. Typical cost of rail is something closer to 250 eur.

This also ignores the speed: if the prices were the other way around, with airfare twice as expensive as rail, I expect most people would still take the plane.

> Madrid-Paris on RyanAir for 50 eur, and for 100 eur on regular airlines

Airlines also typically charge for luggage, RyanAir charge extra for anything they can think of, including choosing a seat, and people booking at shorter notice subsidise those who book in advance. The cost difference for most passengers is probably smaller.

Can you? Seems that connection does not run regularly either when it comes to time (I checked Trainline and on another date there actually was a connection much like that) or for that pricepoint.

10.5 hours is still longer than 2.5 (or maybe - if you include security checkpoint time - 3.5 hours) by plane.

I think you're underestimating the travel to/from the airport. Madrid city centre to airport takes 45 minutes, you should be at the airport at least 2 hours prior to the departure, Paris airport to city centre takes another hour. Even if you're a seasoned traveller who pushes it and come to the airport just one hour prior to departure, you should still count with at least 3h overhead.

Point is: You don't often need to travel to the city center, and choosing that as fictional final destination is giving trains an unfair advantage. Often you need to somewhere NEAR Paris.

Also, and this may be related to the airports I fly out of, but I have hardly ever had planned more than an hour of time from entering an airport terminal to the gate. In TXL (sadly closed now for the much inferior BER), I averaged 25 minutes. At Stuttgart, I once managed to get there in 20. It all comes down to being prepared for security, knowing which security controls are often underused and picking up the right departure times. rel: https://www.youtube.com/watch?v=cnNyUGhXTsw

> Also, and this may be related to the airports I fly out of, but I have hardly ever had planned more than an hour of time from entering an airport terminal to the gate. In TXL (sadly closed now for the much inferior BER), I averaged 25 minutes. At Stuttgart, I once managed to get there in 20.

This is the saddest part of flying, that it really can take only 20 minutes, and instead of making it as efficient as possible, there's the opposite development, where the recommended time has gone from 1 hour to now at least two hours.

Very much depends on whether you need to check in luggage. My guess is that bag drop is closed 20 minutes prior to departure, but I might be wrong. Picking up luggage can easily add 15-30 minutes as well. Even on relatively small airports like Copenhagen, some gates are at least 10 min of brisk walking from the security, so 20 minutes is really pushing it without prior familiarity with the airport. But yes, it can be done.

Paris-Madrid is a poor choice, provided the French and Spanish rail gauge are different, meaning one needs to change somewhere. https://en.wikipedia.org/wiki/Iberian-gauge_railways