He claimed to have trained in Canada (and maybe the UK) but apparently his actual service was minimal. Not that it matters. He wrote about aviation (
Pylon was a racing novel), and never better than in "With Caution and Dispatch," published in the anthology Uncollected Stories of William Faulkner, edited by Joseph Blotner c. 1979.
I found a long-ago excerpt from Esquire in Sept. 1979, which set me looking for the book. Some nice Camel details. Here's a partial text:
Uncollected Stories of William Faulkner - William Faulkner - Google Books