Nonstop from Atlanta to Buenos Aires, 10 hours.
The funny thing is that, for a flight this long, the time difference is marginal (BA is only +1h from EST.) You leave Atlanta late at night (around 11PM, if I remember) and then arrive the next day around 10AM having the opportunity for pretty much a full night's rest.
I did that flight in 2019. Wasn't bad at all, especially with an empty seat next to you.
More worried for New York-Rome in a couple weeks just because I'll have to get to sleep on the plane at like 6-7 PM EDT if I want a remotely decent night's sleep before arriving in Rome at 7:15 AM.
I did Atlanta-Rome last summer and even though I didn't sleep a wink, I thought it wasn't too bad. My return was Rome-New York (which is ~1.5 hours shorter than the ATL route) but felt weird because the entire flight is in daylight and the timing of your two meals (breakfast, lunch) felt off to me.
About 2 weeks ago I did Honolulu to Detroit, which has an 8h50m flight time. That was probably the worst flight I've ever done.
