Recently I flew a red eye DEN-JFK on DL. There must have been about 30 people on a 737-300 so everyone had a row to themselves with nobody behind or infront!

End of September 2001 I flew LAX-SYD on ANZ in C. A 747-400 with about 40 people on it. The return wasn't much busier.

In 98 IAD-HPN on a j31 - just the flight crew and me. I was worried they would just cancel it but there must have been pax for the return!