Statistically Speaking, what is the least busy day of the week for air travel, obviously excluding holidays.?

On top of the least busy day of the week, I wonder what the least busy time of day is. For example, I would think that a flight that leaves around 2pm would be less busy than one that leaves out at 10am to the same destination. I would also ume that Fridays and Sundays are the worst time to fly. I'm most interested in U.S. stats.