Surprising, but if you replay FR24 it got as far as off the coast of Maine near Portland, then turned round and went to Charlotte, overflying Philadelphia en route. Presumably Charlotte had a spare 330 (and crew) available there and Philly didn't. Sounds like out of the box thinking that got them to MAN in the end - I suspect a lot of carriers would have returned to PHL, cancelled the flight and most people would have been home a day late rather than 7 hours. They were only on the ground in Charlotte a couple of hours, which isn't bad considering they had to transfer pax and bags.