My longest flight was from Moffett Field CA, to the Strait of Juan de Fuca, and back to Moffett Field. 14.7 hrs.
The longest commercial flight I can remember is the flight from McGuire AFB to Frankfurt, Germany via Newfoundland and Shannon. A lot of the trip is very fuzzy, I was just a pup. This was before jets made it to the big time. Coming home 4 years later via jet was about 6.5 hrs IIRC, we were diverted to Charleston AFB.
bob