Is AA actually flying the 737 MAX?
According to their website, they will start commercial flights using the 737 MAX on 29 December, but will be testing their aircraft on non-commercial flights before than:

We’ll begin with non-commercial flights in early December 2020 before the official return of the 737 MAX. On December 29, we’ll resume scheduled service with 2 flights a day (1 round trip) through January 4, 2021, from Miami (MIA) to New York LaGuardia (LGA). We expect to phase more of the aircraft into our schedule through January, with up to 36 departures from Miami.

(aa.com, emphasis mine)