Map of the St. Louis area showing the position and track of the aircraft described in the post.

🇺🇸 N655FR - Airbus A321 271NXSL - Frontier Airlines FFT4278/F94278, Harry Reid (LAS) to Washington Dulles (IAD) - 4.3 mi away @ 36975 ft, heading E at 559 mph. Spotted for first time! [03:41:33 AM CDT] #A89FDA #N655FR #A21N #FRONTIER_FLIGHT #FFT4278 #F94278 #ADSB #ADSBbot