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

🇺🇸 N37281 - Boeing 737NG 824/W - United Airlines UAL1883/UA1883 (BWI-SFO-YVR) - 11.9 mi away @ 38225 ft, heading W at 524 mph. Spotted 2x before! [09:35:55 AM CDT] #A43EC3 #N37281 #B738 #UNITED #UAL1883 #UA1883 #ADSB #ADSBbot