I have 2 flights tomorrow from MSY to DFW to London heathrow. I am ticketed as a BA customer but both flights are operated by American.

I cannot check in online. I get a "This itinerary is not supported for check in at this time. Please check in at the airport with an agent."

BA says don't worry about it and check in online. I do know AA has oversold the flight (I have a seat reserved but there is a warning indicating that the flight is overbooked). Is checking in online going to get me booted?

I can't miss that flight to London. I'd have to wait til the next day which would be a disaster.

Is it unheard of if I went to the airport tonight and checked in, in person?