In the final scene Will states that 2977 American lives were lost on 9/11.
Although there were 2977 victims that day, 372 of them were foreign nationals from 90 different countries.
Neal Sampat (Dev Patel) incorrectly references the the Emergency Broadcast System (EBS) which was replaced with the current Emergency Alert System (EAS) in 1994.
The establishing shot of the plane carrying Don, Elliot and Sloan from Washington DC (DCA) to New York's LaGuardia Airport (LGA) shows a 747 with its recognizable second level "bump". The runways at LGA are too short for a 747. The interior of the plane has six-across seating typical of the smaller 737s that actually do operate between DCA and LGA.
Special significance was assigned to having a United Airlines crew operating the flight between Washington DC and New York's LaGuardia Airport. The United flights between those airports are a code-share and operated by US Airways' crews.
Don, Elliot and Sloan are sitting in economy class seating flying between Washington DC and New York's LaGuardia Airport. There would be at least a bulkhead and three rows of first class seating between them, the flight attendant position and the cockpit, making the physical confrontation shown between Don and the flight crew impossible.
Bruno Amato is credited as officer Bello, even though his jacket says Hennigan.