Every day 93 000 flights are starting from approximately 9 000 airports.
At all time there are between 8 000 and 13 000 airplanes in the air.
See them on the video below 3D-Globe “Orbitarium” in Technorama - The Swiss Science Center.

[!]Note: I highly recommend you to switch to full screen to enjoy it at its best:

Civil Air Traffic Worldwide 24h from Thomas Hofer on Vimeo.
Now all I can do is to say WoW!