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

🇺🇸 N12238 - Boeing 737NG 824/W - United Airlines UAL2048/UA2048, Washington Dulles (IAD) to Phoenix Sky Harbor (PHX) - 9.3 mi away @ 38900 ft, heading W at 487 mph. Spotted 11x before! [01:49:27 PM CDT] #A05E02 #N12238 #B738 #UNITED #UAL2048 #UA2048 #ADSB #ADSBbot