Originally Posted by
dtman85
I called United the first time, 20 minutes on the phone, and they couldn't change the FF#. I called in the second times and it only took 2 minutes for the agent to change FF#.
UPDATE: You can now change it online while checking in (I used mobile check-In). I had called United yesterday to change the FF# to MP (it was booked with AC by corporate travel) and I was told "all set" but the change never happened. I planned to change it at the gate but was pleasantly surprised and happy to see the option come up during the mobile checking in process.