Do the skies really need a postal service? The denizens of Air Mail's towns do not, as a general rule, occupy the world's upper atmosphere. The number of times you're actually delivering packages is minimal, and you don't get much of a taste for actual floating cities until the game is nearly finished. But I guess the more accurate title "Air Errand-Boy-turned-rebel-pilot" doesn't exactly roll off the tongue.
Nevertheless, there's something to Air Mail's aviation, which is similar to Pilot Wings, with a touch of Miyazaki's Porco Rosso in terms of style. Taking to the air is as easy as pulling back on your iOS device, initiating lift-off in your rickety seaplane. You can use touch controls for a less authentic experience, though this lessens the thrill of soaring among the clouds somewhat.
Sure, if you've ever played any sort of arcade flight sim you've basically played Air Mail, which boils down to variations on airborne object collection and retrieval, flying through rings and racing down the clock to avoid horrible calamities. But to its credit, the uses of these designs can be inventive. Your ship is outfitted with various attachments that allow you to light ceremonial torches or snip the wires from bomb-carrying transports.