I've recently been thinking about flight length in relation to sleep and fatigue/exhaustion. Here are a couple of example flights:

A flight from New York to London takes about 7 hours. If it departs at 11 pm New York time, it arrives at 11 am London time.

A flight from Rio de Janeiro to London takes about 11 hours. If it departs at 11 pm Rio time, it arrives at 2 pm London time.

Now, my mom and I have a disagreement as to which flight would leave one more exhausted. My mom thinks that since the quality of sleep in-flight is inferior to that in a regular residence, the shorter flight would allow her to get better quality sleep in a regular bed quicker than the longer flight. On the other hand, I tend to think that the shorter flight allows for less time to sleep, thereby making one more exhausted/fatigued upon arrival compared to the longer flight.

Who do you think has a stronger argument here?

TATL flights in the 6 to 7 hour range are brutal. Very little opportunity for sleep, and you arrive in the morning basically exhausted when everybody else is waking up. I much prefer a longer TATL flight. Last one I took was IAH-FRA, and I thought that was just about the right length.

Go agree. The longer flights are better as you have more time to sleep. The only TATL short flight I didn't mind left NYC in am and arrived in London pm so I could go to bed right away rather than struggle through the whole day exhausted. Of course, a whole day was shot.

Leaving BGI on a warm evening and arriving in LHR 7 hours later on a cold winter morning is the worst.

Agreed. TATL flights in the 6 to 7 hour range are brutal. Much rather go the other way in 10+ hour flights to Asia.

I also agree. I'd rather have flights up to 6 hours, or above 10 hours. It's impossible to relax on the east coast>europe flights.

Also, I found that my KIX-IST overnight (departure ~22:00, arrival around 05:00, duration about 12 hrs) was also very good as far as getting me the needed sleep.

The only counterargument I have is that on an AUH-FCO 6-hour flight that I took in January, I slept for maybe 5.5 of those 6 hours and was feeling quite refreshed in FCO. The flight departed AUH at 3AM, so maybe that's why I fell straight asleep as soon as we were wheels up.

Want exhaustion? Try 5 hr red-eye to West Coast from Hawaii, followed by another flight to the final destination. Best 2nd flight: 10.5 hours to FRA in F.

IMHO opinion, the only flight worse that east coast to Europe is an early-mid afternoon departure, DFW to Europe. It leaves too early to get any sleep, and then still gets to Europe early in the AM.

I tend to agree. But for those of us on the east coast, there's no real alternative unless you want to loose a whole day. I try to take the last flight out, thereby getting into LHR as late as possible. I find it's much easier to stay energized after the flight from 10-2000 as opposed landing at 6. Those four hours make a HUGE difference IMO.

I'd rather lose the day than deal with the overnight flight.

I think it depends in part on the class in which you are sitting. Being in coach will be difficult to sleep no matter which option you pick.

Actually, believe it or not, some of the best sleep that I've had was in coach, rather than biz in some cases. It really depends on how tired I am and how close to bed time the departure time is.

In the OP's example, the GIG-LHR flight gets to LHR late enough so that you only have a few hours to stay awake before nightfall (and sleep in a real bed).

The longer the flight, the better the Ambien works! If not, be prepared to be well rested before your flight.

A few days ago I did a redeye SFO-DFW. Now that was a bad idea.