Not just "some airlines"; specifically, Emirates does this. And guess what? They did this to us when we missed our connection in London - this was twenty years ago, but makes my blood boil even today. What takes the cake, though, is that a) we missed the connection because Virgin took off late from Orlando that caused us to miss our connection and, more importantly, b) Emirates staff put us through to Mumbai on Kuwait Air ex-London. So, they knew that we had continued on our flight but STILL cancelled our return, confirmed trip. I had to make an overnight journey (each way) to Mumbai to go to the Emirates head office to get our tickets reinstated. We lost our window seats and our meal choices in the bargain :-(