Hmm... did the plane have a dark blue tail? It could have been a United Postal Service plane. The plane could have also been Kitty Hawk. From the flight description you gave, maybe it did not fuel up enough? It has happened. A relative of mine was on a Continental 727-200 flying from EWR to SJU when the plane turned back to EWR because they needed more fuel. Maybe there was actually a problem with the plane? I'm not really sure. Hope this helps somewhat :-).