10 hours 35 my longest, Calcutta to Penang. On the day of an Atlantic crossing, Iceland to Canada would have been possible, lovely tailwind, but I went into Narsaauaq just to put it 'up my sleeve.' This proved useful in later Bizjet days. The drums in the fuselage would start to cough at 4 hours, helped keep one awake. Requests for the other seat always turned down, seat much more useful for picnic from hotel. Long before SatNav days!
I remember the big-engined Land Rover at Stanley which might evoke a memory for a previous correspondent.