Diagram of routes from Croydon aerodrome. Views of Croydon aerodrome. Planes, including the Heracles, come in to land.

Letters are written and air mail labels stuck on, post boxes for air mail in the City, a messenger boy arrives with an airmail letter just as the postman is collecting them.

Mail from the box arrives at the sorting office. The letters are first arranged to face the same way up in order to cancel the stamps. Air mail collected from general post boxes is separated from inland mail. Awkward-shaped parcels have their stamps cancelled by hand.

The letters are sorted first by country, then by town. After tying into bundles, the letters are put into sacks and labelled. The mail van sets out for Croydon. Letters which have missed the collection can be phoned through to Croydon. Shots of the mail van en route and planes getting ready for take off at the aerodrome. The mail van arrives and the bags are loaded into the plane. The ground pilot signals for take-off. The plane, a Heracles, revs up and takes off.