It's function on cars was to see behind it, but this feature is not seen on airplanes, being, in actuality, the wings themselves. It is believed that the rearview mirrors may have gotten larger and larger over time in order to see more behind the car. Meanwhile, natural selection was making this feature aerodynamic and as the rearview mirrors got larger and the cars' speed became greater, the mirrors provided lift for the car that enabled it to glide short distances. This provided a huge selective advantage and it was only a matter of time before cars became planes. The fossil record for airplanes is quite diverse and seems to indicate that the aeroplane family tree may not be so simple as we wish it to be.
Some specimens are even bizarre.
Some earlier aeroplanes have been named patriaeroplanus africanus because they were found in North Africa and have been dated to circa 1942. An odd characteristic is that many are found with strange circular punctures in the metal skin. Other similar fossils have been named japanicus, europus, americanus, and the abundant luftwaffecanus found with trademark swaztikas over regions of europe. All have been dated to the similar time frame of africanus and show similar punctures. A few very ancient specimens have been found that may date back to the 1910's.