Of course flights are subject to delays, and booking a flight due to land an hour before Shabbos is just asking for trouble, which is why there were probably no shomrei shabbos on the flight that got the “heter” to land on Shabbos. But “double the time” for a flight makes no sense at all, anyone who promotes it is an idiot, and anyone who claims it’s a din is forging the Torah. <i>A fifteen-hour flight is no more subject to delays than a one-hour flight</i>. Unlike a car, once a plane is in the air it’s not affected by local weather. On the contrary, the longer the flight the more opportunity there is to catch up by flying faster if you catch a good wind. Either 5 hours is enough buffer time for a one-hour flight or it’s not; but if it is then it must be enough for a ten- or fifteen-hour flight. And to claim that a fifteen-hour flight needs a fifteen-hour buffer is ridiculous.
Those who flew on the 6:30 flight, due in at 11:40 Friday <i>morning</i>, obviously believed 5 hours is sufficient allowance for delays. In this case it proved inadequate, but what would you say if they’d left 10 hours and the flight ended up delayed 11? You’d be saying the same thing no matter <i>how</i> long they left. What are they supposed to do? For a lot of people it’s not practical to leave on Wednesday; they’re in NY to do business, to work, to have meetings, to do whatever, and you can’t tell them to lose the whole Thursday as well as Friday.