This November 2019 video says about itself:
List of 10 Highest Flying Birds In The World By Flight Height
Bar Headed Goose
Another, 6 November 2018, video used to say about itself:
Bird flight height comparison:
Migratory birds and birds of prey can reach substantial heights while flying. This list gives the highest recorded flights for various species (limited to observations of 4,500 metres/15,000 feet and above).
Here is the list of some of the highest flying birds in the world: