Most airlines have a "interline" aggreement. It allows passengers inconvenianced from one airline to be rebooked on another. Basically the airline they were on that is delayed, cxld, or what not books a seat on that aircraft. They do this because all the airline's computers talk to each other. So one airline can book you for any other airline. So if you are moved to another airline your ticket value is absorbed by your airline you were originally on and then they must pay a contract fee to the airline they rebook you on. If you have one of those cheap airline fares like expedia, than a rebook isn't possible unless the airline issues you a FIM (Flight Interruption Manifest). This is the only way you can transfer those.
They used to do it by the weight of tickets. They would weigh all the tickets that were rebooks due to pax inconveniance and whoevers weighed more got money from that airline.
The flipside, is if you do not have an interline agreement like B6
, and other LCC's do not. You can't be rebooked to them or off of them to an airline. So you are stuck. It is a gamble you take, and they will eventually get you to where you are going, but I have dealt with passengers purchasing tickets for same day travel because WN
, screwed them at KORF.
Something you might not know though about ticketing is if you purchase a full Y or expensive fare ticket, you can actually walk up to any airline and ask if this is good on them. The airline could actually accept it and book you on them and take the cost of your ticket. In short who ever has your PAPER ticket gets the money.