How many planes are in the air on average at one time?

Question

How many planes are in the air on average at one time?

Answer 1

The number varies depending on the time of day...

Here's a cool video that gives some idea to flights over the course of the day in the US:

http://youtube.com/watch?v=dPv8psZsvIU

At this very instant (10:49pm Eastern Standard Time), the FAA is tracking 3,213 airborne aircraft and there have been 42,520 arrivals in the last 24 hours.

Here's another good site that has flight tracking info for the US. Unfortunately there isn't a similar site for the entire world.

http://www.flightaware.com