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

🇧🇷 PR-VBY - BOEING Boeing 737NG 73A/W - Alaska Airlines ASA455/AS455, San Francisco (SFO) to Washington Dulles (IAD) - 5.1 mi away @ 39200 ft, heading ESE at 570 mph. Spotted for first time! [04:19:14 AM CDT] #A9E8CE #PR_VBY #B737 #ALASKA #ASA455 #AS455 #ADSB #ADSBbot