Airmail is a form of postal mail that is sent by airplane. It was first seen in France which is why all Airmail has the postmark words 'Par avion' on it. In the French language this phrase literally means 'by airplane.' When Airmail is sent overseas, the length of time it takes to get there will vary. Airmail that is sent fro the USA to the UK can take as long as 10 business days to arrive.