What's the highest altitude ever reached in a jet, and when and in what jet?

Answer 1

Hope this helps...

The highest altitude obtained by a manned air-breathing jet propelled aircraft following an uncontrolled ballistic trajectory is 123,523 feet (37,650 m) set by Alexandr Fedotov, in a Mikoyan Gurevitch E-266M (MiG-25M), on 31st August 1977.

The highest altitude obtained by a manned air-breathing jet propelled aircraft in controlled horizontal flight is 85,069 feet (25,929 m) set by Robert C. Helt and Larry A. Elliott, in a Lockheed SR-71, on 27th/28th July 1976.

Answer 2

The highest and safest altitudes are not the same. In general, an aircraft is more unstable when flying at its maximum altitude. The service ceiling of the 747-8 is 43,000 feet. A service ceiling is the altitude beyond which the aircraft cannot climb at a useful rate (that is, its climb rate is less than 100 fpm above the service ceiling). A 747 can thus fly higher than 43,000 feet, but it would not climb at a useful rate beyond that altitude. Going slightly higher has no dramatic effect. Once the aircraft reaches its ceiling, it won't climb any higher, period. Some aircraft are less stable when they are at their absolute ceilings—this is sometimes called the "coffin corner" because the difference between stalling and overspeeding can be very small.

Answer 3

as of 2001
http://www.wired.com/news/technology/0,1282,46054,00.html

http://www.answerbag.com/q_view/7433

this one I see no altitude numbers on but it should be able to go very high.
http://news.bbc.co.uk/2/hi/science/nature/4019663.stm