I diverted a BA 777 into Memphis in 1999... was due to the complete closure of DFW airspace due to thunderstorm activity, and San Antonio and Houston (our usual alternates) being slap-bang in the path of the oncoming weather. The skipper had headed off to Heathrow instead of Gatwick, so was late for report, and as the operating Co-pilot, seeing the magic four letters TSRA on an American TAF (translates as "chaos possible, cover your ass") I'd tanked about 8 tonnes over the flight-plan figure, so we were always comfortable for fuel.
The full tale is long, and very interesting, but effectively a lot of favours were called in that night by BA staff at Dallas, and we effected a recovery to DFW right on the trailing edge of Flight Time Limitations. I think we were the first 777 Memphis had seen, and certainly the US Customs were decidedly less than helpful, refusing to allow any crew-member off the aircraft to carry out a walkround until the folly of that position was pointed out.