K.S.
When our son turned 4, we started taking a red-eye flight for our yearly vacation (total of 3 times). We had a short flight first that put us into Denver around normal bedtime. We then get him to curl up on the floor at the airport with his blanket and fall asleep. We just carry him onto the plane, buckle him in and he sleeps the whole way. The flight out of Denver left at midnight and put us at our destination around 6:30am at which point we had to wake him for customs/immigration. He was groggy but in a good mood because we were at our destination.