accident investigation, CRM, aircraft performance, general management
Only the last of those being a degree subject. CRM could reasonably be regarded as an extension of psychology, and the others of aeronautical engineering.
But, as I said, be very aware both of the shelf life of knowledge, and that most degrees are not qualifications to practice. They are essentially routes into the most junior roles of professions, from where someone starts really learning. They are not equivalent to the specific qualification that is a pilot's licence. Hence my advocating skill and licence acquisition, rather than education, for this oft-mooted "backup".