My personal record for a trans-con flight is SAN-EWR in four hours and fifteen minutes, equating to a ground speed of +/- 570 mph/912 kph. January, 2002, a Continental red-eye flight: as we taxiied out for take-off, the captain told us to expect some turbulence, but also, as he put it, "some incredible tailwinds! I know most of you will want to sleep, but if you do get up, be aware that it could hit at any moment, and to keep your seatbelt fastened, obviously!"
The return PIT-SAN took nearly five and a half hours, equating to a ground speed of +/- 383 mph/613 kph. I don't know how else to explain it, but, it even felt like we were going slower. I could just sense the power of the wind, like trying to walk in a hurricane. No diversions, no real turbulence, and no issues - but it felt metaphorically like a "slow boat to China".
You brought back memories of my two personal records...
1. AA049 BOS-LAX on 17MAR80 on a 707-123B: this flight wound up being an incredible tally of coincidences as it turned out years later to be my last-ever flight on a 707 (the final item); we had 80mph headwinds which resulted in a 7h53min flight time (so my longest-ever trans-con), but we didn't mind one bit as we were in F and the cabin crew delivered an outstanding dinner service (more leisurely than normal) but the additional coincidences were that it was St. Paddy's Day (AA had loaded special green shamrock swizzle sticks for F) and the entire cockpit crew were Irish to the point that the F/O's last name even was Ireland!
2. UA052 LAX-IAD on 29NOV81 on a DC-10-10: another string of (fewer) coincidences...my first aborted takeoff (faulty warning light on no. 2 engine generator); then after the 2nd attempt, while making the turn over Long Beach to head east, the captain told us we were going to have incredible tailwinds with an expected VERY early arrival while the cabin crew were already starting the breakfast service and the movie so they'd have time to do the later deli-buffet service (this was also in F...ah, UA's old "Ocean to Ocean Service"!) which as I recall they started setting up immediately after collecting the serviceware from breakfast (WAY early!). Then IIRC somewhere mid-con., the captain came back on telling us we were indeed experiencing 200mph tailwinds which was making our ground speed supersonic! I have it recorded in my flight log that the flight was a mere 2hrs 50mins! The cabin crew were running around like chickens without heads collecting the last serviceware while we were on short-final to IAD! Needless to say my fastest-ever trans-con, and I'm sure an unofficial speed record (at least at the time)!