On a Wing and a Wave
One of our Darkisle reources¸ designed for use with a 1920s British Call of Cthulhu campaign in mind¸ but generic enough to be used in other settings or with other games set during that era.
On a Wing and a Wave describes a small airline operating a single flying boat to a remote backwater. Full technical details are given for the Supermarine Sea Eagle¸ a real aircraft of the time¸ with two suggested liveries and a mono line diagram to use if you want to design your own.