The RAF had escape pattern flying boots[0] from from mid-war. Looked like a normal shoe with sheepskin lined legging attached. You cut the top off with the included penknife to leave a normal looking shoe[1]. The leftover bits were designed to reassemble as a waistcoat if you needed to sleep rough.

Wouldn't be surprised if USAF had similar or maybe he was issued an RAF pair for having difficult feet. :)

[0] https://www.historicflyingclothing.com/en-GB/ww2-raf/raf-194...

[1] http://www.oldnautibits.com/assets/images/aeronautical/image...