how many domestic US flights are there each day?

Answer 1

In May 2006 (the most recent data available) we had 875.5 thousand domestic flights (source - bureau of transportation statistics - http://www.bts.gov/press_releases/2006/bts038_06/html/bts038_06.html.) Divide it by 31 and you'll get about 28,250 flights per day on average.