The Rüppell's vulture of Africa lays claim to being the highest flyer with confirmed evidence of flight at an altitude of 37,100 (mid air with a jet requiring engine shutdown - previous record had been a mid air at 21,000 with a Mallard).
https://en.wikipedia.org/wiki/R%C3%BCppell%27s_vulture
Bar Headed Geese migrate across the Himalayas at 29,500.
https://www.scientificamerican.com/a...ans-of-the-sky