Several recent press reports tell of supposedly "nonstop" flights from Europe to the U.S. East Coast that couldn't make it against seasonal headwinds and had to stop to "fill 'er up" at Goose Bay or Gander in Canada. The stop generally results in a delay of at least two hours—always a nuisance, and a real problem if you have a connection.
The problem seems confined to 757 flights. That venerable plane, a mainstay of transcontinental nonstops, was not really designed for transatlantic flights. But it's the smallest plane that can make it across the Pond at all, and airlines have found that it's the right size for routes with insufficient traffic to support flights on the larger 767s or A330s, planes that really do have reliable transatlantic range.
No relief is in immediate sight for travelers on those "long, thin" routes. Boeing designed its new 787 as a "long, thin" plane, but even it holds more passengers than the 757. In the long run, airlines that operate the 757 are counting on the new generation A320neo and 737max models to gain enough additional range through engine improvements to allow reliable transatlantic nonstops. But those planes are many years in the future.
Clearly, if you have a choice—and especially if you have to make a connection on the East Coast—you should try to avoid 757 flights. In addition to iffy nonstops, those planes generally feature some of the worst economy seating in the air.