As we can see by many of the previos statements "longest flight" is pretty open ended. Narrowing down the battery is a good start, but still, a HUGE amount will come down to flight style. I tried to max my flight time on my odl twin boom. after 30 minutes, it was miserable. A blue sky, with a single plane, flying in straight lines. At that point, it becomes as much about the stamina of the pilot, as it does about motor/prop/battery/airframe cominations. Now that I have an Ardupilot, i'm more interested in it than ever! It can maintain the stable, gentle flight needed to stay aloft long term, and I don't have to stare at the sky beyond my own A.D.D. limits. LOL! I know some of the guys at DIY Drones have dabbled with gliding, but I want to see how long a non-exotic airframe can stay aloft under power. There was a guy at Flite Fest with a twin engine profile seaplane. (CraftyDan, which vendor was that next to the build tent?) He had a BIG plane, with blue wonder motors. I asked him about flight time, and he had estimated about AN HOUR! He said he only flew about 15 minutes at a time, but could do that 4 times without recharging. LOL!
Is THAT the original spirit of this concept?
I do think distance and time need to be kept separate though. While not gliding, there is still a huge difference between going really far, and staying in the air a very long time. I have seen some slow poke undercambered planes that fly on little more than a breath. BUt I have also seen some relatively fast planes with very impressive glide rates.