It's really quite incredible how many airplanes are in the sky at any given time.
It's interesting to me how they sometimes leave clouds (CHEMTRAILS! NO COMMERCIAL FLIGHTS OVERHEAD!) in their wake.
Air travel is a significant contributor to carbon emissions, but not many people pay mind to it—the only lasting evidence that's sometimes generated is a harmless cloud that disappears within hours.
(Actually taken at 7:08 AM—forgot to deactivate DST on my camera.)