This exceptionally fast-moving upper-air flow has been naturally utilized by the eastbound flights. For example, flight PO968 from Seoul to Anchorage recorded ground speed of 677 knots (779 mph/1254 km/h)!https://t.co/N3EPcc2QbT pic.twitter.com/pci7jpVAbZ

— Mika Rantanen (@mikarantane) October 13, 2019