With the airlines, they often will not say that a degree is mandatory. However, the minimums being posted by the airlines for hire is not the typical person getting hired.

So, though they may not say a degree is required, there is a good chance that you won't get an interview without a degree if the bulk of applicants have one. If you do get a degree, I would suggest not getting an aviation one, as you would not have a fall back plan. Also, the aviation degrees cost a lot more. The airlines don't usually care what your degree is in, they are more interested in whether or not you have one.

ATP is an airline transport pilot rating. You have to have 1,500 hours of flight time before you can take the checkride for one. The checkride isn't so bad, but the written test is a pain in the butt (I am studying for it off and on right now). FE is flight engineer rating. I think you only have to take a written test for that rating.

I hope this all helps.