The arrival of a severe winter storm on Thursday was not a surprise.

With a snowstorm ominously described as a bomb cyclone bearing down on the New York area, the Port Authority started warning about airport disruption and flight cancellations on Wednesday afternoon. On Thursday, as the snow piled up and winds strengthened, the Port Authority announced that Kennedy would temporarily shut down. At 1 p.m., it was telling travelers that it intended to resume flight activity later that day.

Around the world, airlines were reading that forecast as a green light to take off for long hauls to New York City. As late as 6:20 p.m., the Port Authority was still sending out tweets that it expected to reopen Kennedy that night. But an hour later, close to 7:30 p.m., the Port Authority decided to keep Kennedy closed until Friday morning. That meant that all of the flights bound for Kennedy had to divert to other airports or turn around.

The sudden, unplanned detouring of all of those planes set off a chain reaction that stretched to various continents and left Kennedy tied in knots for the next few days, with passengers stranded in overcrowded terminals and on planes.

“Virtually no foreign airline canceled any flights into J.F.K.” on Thursday, said Jason Rabinowitz, a freelance aviation blogger who tracked the cascading pileup as it played out. “They all launched their aircraft, but by the time they got halfway over the Atlantic, they found out they couldn’t land at J.F.K.”

As an example, Mr. Rabinowitz cited Iberia Flight 6253, which got halfway to New York from Madrid before making a U-turn and going back to Spain: an eight-hour fight to nowhere. Norwegian Air Flight 7019 made a similar journey Thursday night en route to New York from France. “That was kind of weird,” said Mona Bismuth, 27, a passenger. “We turned around at the southern tip of Greenland.” A passenger on a different flight was sent back to Moscow — twice — because of what was happening in New York.

When Kennedy gradually reopened on Friday, the airlines started sending their diverted planes on to Kennedy. The airport’s runways could handle the traffic, but some of its terminals were quickly overwhelmed with planes arriving faster than gates could be cleared for them.