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

🇺🇸 N721NK - Airbus A321 271NXSL - Spirit Airlines NKS991/NK991, Chicago O'Hare (ORD) to George Bush Intcntl/Houston (IAH) - 4.0 mi away @ 34500 ft, heading SSW at 505 mph. Spotted once before! [10:27:09 PM CDT] #A9A879 #N721NK #A21N #SPIRIT_WINGS #NKS991 #NK991 #ADSB #ADSBbot