What is the origin of aero?

Aero is from Greek 'air'. So aero is anything pertaining to the air or aviation.

Check this for example: aero-, aer-, aeri- ( origin, Greek: air, mist, wind).

There is a difference though. Airplanes are the ones such as the Wright Brothers first airplane to fly and glide only, while aeroplanes refer to the later and present days jet powered aircraft. So if you wanted to study about aeroplanes you would first have to go back into history and read about how airplanes brought it all about. Paper and wooden toy airplanes started it all off with them just gliding through the air once thrown upwards by both kids and adults alike.