While no official announcement seems to have come down the pike, United Airlines’ only flight out of Oakland – a daily OAK-DEN Airbus – no longer shows up in availability beginning with the summer schedule on June 5, 2012.

The last flight with seats for sale is UA352 on June 4 departing Oakland at 5:30am and arriving in Denver at 9:00am. A hat tip to Steve Tao’s tweet sent me over to this Airliners.net thread discussing the topic a couple of days ago and I’m all but convinced I can leave a question mark off my post title.

As the second poster in that thread mentions, Southwest Airlines ramped up DEN-OAK service to four times daily and given OAK has been such a Southwest stranglehold for ages, it really doesn’t come as a surprise. Except maybe for the fact that United isn’t replacing the service with Express flights.

A combination of competing service from United’s San Francisco hub next door, the carrier recently dropping OAK-LAX service and continued pressure from Southwest have probably made OAK a loss maker for some time.

I will happily eat my words and apologize to United and their Oakland employees should they simply be too busy fixing the bugs from the March 3 system conversion to have loaded in new United Express service. I don’t think I’ll have to, though.