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

🇺🇸 N538AS - Boeing 737NG 890/W - Alaska Airlines ASA15/AS15, Ronald Reagan Washington Ntl (DCA) to San Diego (SAN) - 4.3 mi away @ 37150 ft, heading W at 503 mph. Spotted once before! [10:36:39 AM CDT] #A6CE36 #N538AS #B738 #ALASKA #ASA15 #AS15 #ADSB #ADSBbot