AACK!! Scary to see that we were so far into the pages. Here's a guess: how about Eastern Airlines?
They sponsered "If You Had Wings," which opened less then a year after MK opened, which was replaced by "Delta Dreamflight," which was replaced by "Disney's Take Flight," which was replaced the the current..."Buzz Lightyear's Space Ranger Spin."
However, I don't know if they were the first offical airline. Just anther chance to throw out Disney history!!!