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

🇺🇸 N8921Q - Boeing 737MAX 8 - Southwest Airlines SWA2947/WN2947, Denver (DEN) to Washington Dulles (IAD) - 4.0 mi away @ 34600 ft, heading E at 555 mph. Spotted 21x before! [10:50:54 AM CDT] #AC4F4C #N8921Q #B38M #SOUTHWEST #SWA2947 #WN2947 #ADSB #ADSBbot