Just going off Goodreads.com since they do not recognize books without ISBN numbers, which is about half the books I read. So here is what I might have said about some books I am finishing from the 1930s. All are nom de plumes of Eileen Hemng (born Marsh). She lived near Lymphne airport, Romney Marsh and though could not fly was fascinated by it. She wrote 120 books in 15 years under 18 different names. She mentions her village Aldington as a kind of signature, which happens in both of these books.
1. Secret of the Desert by Guy Dempster, Lutterworth. 1939 A flying tale set in Sudan in 1939 about a crazed westerner trying to clear white folk out of Africa then attack Europe. I wonder who inspired it? Side story of a young boy rediscovering his father. The villain has an underground factory supported by African slave labour building a wide range of aircraft, the one's illustrated looking like Defiants.
2. Flying for Ethiopia by E Martin Shard, Popular Press, no date stated. A not dissimilar story of building up the Ethiopian air-force for Haile Selassie. This is an unusual pen-name for Marsh/Heming
Both stories have high adventure, inspired by W E Johns of Biggles and Worralls fame. Some sentiments would be declared not politically correct today, but were typical of the time.
I am reading a similar story by someone else, David Lindsay. Wings over Africa. It is not formally dated but there is an internal date of 1935 (not proof of the year of writing). The Italian campaign against Haile Selassie in Ethiopia/Abyssinia was clearly causing some excitement. This was part of "The Ace Series" which include some of W E Johns' early Biggles stories. The Lindsay book features a WW1 flying ace helping out the Ethiopians. Despite this the story is full of negative racial/racist stereotypes and black African lives are clearly regarded as of little or no value, hundred mowed down with a machine gun with unseemly rejoicing. The attitudes as well as the biplane were relics of the first world war as middle aged former fliers tried to place their memories into contemporary conflicts.