My company (1,000+ employees, most of them in the NY & SF areas) has a deal with AA. Everyone at a certain level (about 200-250 people currently) gets space-available upgrades -- we're told by the corp. travel agent that we rank in priority equal to their lowest-level elites. Of course, a few people at the highest level are treated like mid-level elites. We don't, however, get a break on fares.

Last month, when there was a managers' meeting in SF (75 people flying from NY, 15 from DC, 20 from LA), the NY-SF travel (as picked by the flyers, not the company) was split 1/3 each among AA, CO & UA.

Since we don't have offices in Chicago, Denver or Miami, I'm guessing that we don't have a large # of Mileage Plus elites. To me, that means a lot of people chose coach (or their own MP upgrades) on UA over the chance of an upgrade on AA for the old-fashioned reasons: convenience, service or miles. Personally, I'd rather fly AA than US or TW, but that's about it.