I've played around with the mantreads attribute using the add_attributes trigger thing in hammer.
Its my experience it is NOT air acceleration. Rather it lets you change air direction easier with just WSAD. With extreme values you can basically stop mid air then reverse backwards, but not at any great velocity. That being said it is still extremely powerful for aggressive strafing.
That's exactly what I hoped for. Now market gardening and rocket jumping on pubs will be even easier and even more fun!