From the Delta website:

" Graduate of a four-year degree program from a college or university accredited by a recognized accredited organization
Degrees obtained from a non-U.S. institution must be evaluated for equivalency to U.S. degrees by a member organization of the National Association of Credential Evaluation Services (NACES)

Postgraduate education will be given favorable consideration. "

I just got back from a family vacation and had the opportunity to speak with the first officer on my leg from atlanta. He specifically told me that his masters degree is what got him the job and highly recommended that i do the same. Everybody has a bachelors degree, so a masters sets you above the competition. While i have no personal experience with this, I figured i would pass on what I was told.

But as rickair7777 said, it appears to be all about connections and networking.