How many airplanes are in the sky at a time?

This question has been long hounding me. Finally I'm able to search for it, and came across this interesting video from Youtube - a graphic description of global air traffic over a 24 hour period. In this map, Europe, US and East Asia are the areas with most air ship travels in a day. Interestingly, the tiny Philippines chunk in this map is covered with yellows - could they be Road Traffic Monitoring chops, or Abu Sayyaf Monitoring aircrafts? LOL.