I once spent 22 of 24 hours in the air from Saudi Arabia to the west coast of the US.
That was extremely difficult, because I spent most of it on military crew (netted) seats, and I can't sleep while sitting.
At least on the MAC aircraft there is legroom, or cargo room if on the jump seats... just don't forget yer woolies.
You can't? I found that if you lay your head on your reserve, prop your rifle case against your leg, and close your eyes, it is possible to sleep for eight of the ten minutes before you jump out of the airplane.