I would say major in a degree that not everyone and his brother is doing, but one that teaches a skill. Civil engineering, construction, fire protection. In my city, any new construction over a certain size requires a sprinkler system. We are talking townhouses, or multi-family units over a certain size. I would say computer science as well, but you really don't need it to learn to code. Getting an education AND a skill is vital when aviation has its cyclical downturns.
I know a guy who was a good carpenter and did nothing but custom woodwork for the well to do. He owned a couple of airplanes. Loads of people are always looking for a skilled handyman, even if you don't get a contractor's license. My next door neighbor hired a guy @ 25/hr, just to fix some sprinklers, patch a wall, and fix a toilet--5 hrs work! My good friend finds old junk motorcycles, fixes them up, and sells them to the rich as a one of a kind toy. He even found a junk frame that was owned by Steve McQueen!
You need the degree to punch the card to get a good airline job, BUT you need a skill to ensure you against down times and to give you the fortitude to stand up to mgmt. bullying tactics.