So there's actually Amadeus, which is the biggest provider in that category worldwide, based out of Madrid: https://en.m.wikipedia.org/wiki/Amadeus_CRS https:/

So there's actually Amadeus, which is the biggest provider in that category worldwide, based out of Madrid: https://en.m.wikipedia.org/wiki/Amadeus_CRS https://en.m.wikipedia.org/wiki/Amadeus_CRS However, train travel isn't really properly integrated as far as I can tell.