A US Airways 767 (N652US) enroute from London Gatwick to Pittsburgh (US #741) diverted into Bangor International Airport Maine at 1400 on Monday 9/18 due to a medical emergency. The aircraft was on the ground about 30 minutes while paramedics attended to the victim who had been having trouble breathing for the previous 3 hours. A landing in Iceland was ruled out due to weather. After conferring with a doctor on board and the ill passenger, Gander was overflown and Bangor was chosen as the diversionary field. After the passenger was taken off the aircraft, Flight 741 continued on to PIT and arrived about 45 minutes late.