About 30,000. The following is an excerpt from: http://www.natca.org/mediacenter/bythenumbers.msp#1 "On any given day, more than 87,000 flights are in the skies in the United States. Only 35 percent, or just over 30,000 of those flights are commercial carriers, like American, United or Southwest. On an average day, air traffic controllers handle 28,537 commercial flights (major and regional airlines), 27,178 general aviation flights (private planes), 24,548 air taxi flights (planes for hire), 5,260 military flights and 2,148 air cargo flights (Federal Express, UPS, etc.). At any given moment, roughly 5,000 planes are in the skies above the United States. In one year, controllers handle an average of 64 million takeoffs and landings. For every one flight you see listed on an airport monitor, two you don't see show up on air traffic controllers' screens. It would take approximately 7,300 airport terminal monitors to show all the flights controllers handle in a single day and approximately 460 monitors to show the number of flights being handled at any one time."

airplanes fly at different altitudes in different airspaces (places around the country) and in all 4 different directions. heres a simplified example. going east there are appxly 10 different flight levels. lets say every other odd number from 21, 000 ft on up. 21, 25, 29, 33, 37, etc thousands of feet asl(above sea level). going west there are appxly 10 different flight levels. lets say every other odd number from 20,000 ft on up. 24, 28, 32, 36, etc thousands of feet asl. going north there are appxly 10 different flight levels. lets say every other odd number from 23,000 ft on up. 27,31, 35, 39, etc thousands of feet asl. lastly , going south there are appxly 10 different flight levels. lets say every other even number from 22,000 ft on up. 22, 26, 30, 34, 38, 3tc thousands of feet asl. if you study this...you will see that minimum seperation is at least 1000 ft in any direction. going in opposite directions ,flights are usually routed into air corridors to keep minimum seperation of at least several miles horizontal and at least 1000 ft vertical. so, even with 5,000 plus commercial flights in the air at any one time over the whole usa...thats a pretty slim chance of intrusion into another aircrafts safety zone. plus with the air controllers, pilots and computer avoidance equipment... the situation is sager than on the local freeways. over the whole usa blessings, dr james retired cfo, pilot and air surgeon

37,000 per day. FAA statistics say there were 13,531,058 Air Carrier flights in 2008. I divided by 365 days. Probably less days which would mean more per day. 156,000 total flights per day. (56,823,081 total in 2008) 183,000 total flights per day based on the last 18 year average. 1,204,006,309 total operations since 1990. That's because there are 10 million less flights per year now than 18 years ago due to gas prices. Most the loss is in general aviation or in other words guys who aren't paid to fly but do it for fun, for sport, because they love it. This is where our future pilots come from. If 10 million less flights means that many less pilots are being trained. The airlines are going to be faced with both a gas and pilot shortage over the next few decades.

Between 28 000 and 39 000 depending on the day of the week.