The highest-flying bird ever recorded was a Ruppell's griffon, a
vulture with a wingspan of about 10 feet; on November 29, 1975, a
Ruppell's griffon was sucked into a jet engine 37,900 feet above the
Ivory Coast--more than a mile and a half higher than the summit of
Mount Everest. The plane was damaged, though it landed safely.

See:
http://magazine.audubon.org/birds/birds0011.html

denny