  with respect to aircraft performance, a ceiling is the maximum density altitude an aircraft can reach under a set of conditions, as determined by its flight envelope. ==service ceiling== the service ceiling is the maximum usable altitude of an aircraft. specifically, it is the density altitude at which flying in a clean configuration, at the best rate of climb airspeed for that altitude and with all engines operating and producing maximum continuous power, will produce a given rate of climb (a typical value might be 100 feet per minute climb or 30 metres per minute,faa "pilot's handbook of aeronautical knowledge" (faa-h-8083-25a) or on the order of 500 feet per minute climb for jet aircraft). margin to stall at service ceiling is 1.5 g. the one engine inoperative (oei) service ceiling of a twin-engine, fixed-wing aircraft is the density altitude at which flying in a clean configuration, at the best rate of climb airspeed for that altitude with one engine producing maximum continuous power and the other engine shut down and feathered, will produce a given rate of climb (usually 50 feet per minute). however some performance charts will define the service ceiling as the pressure altitude at which the aircraft will have the capability of climbing at 50&nbsp;ft/min with one propeller feathered. ==absolute ceiling==  the absolute ceiling, also known as coffin corner, is the highest altitude at which an aircraft can sustain level flight, which means the altitude at which the thrust of the engines at full power is equal to the total drag at minimum drag speed. in other words, it is the altitude where maximum thrust available equals minimum thrust required, so the altitude where the maximum sustained (with no decreasing airspeed) rate of climb is zero. most commercial jetliners have a service (or certificated) ceiling of about  and some business jets about .see e.g. bombardier global express xrs specifications. while these aircraft's absolute ceiling is much higher than standard operational purposes, it is impossible to reach (because of the vertical speed asymptotically approaching zero) without afterburners or other devices temporarily increasing thrust. flight at the absolute ceiling is also not economically advantageous due to the low indicated airspeed which can be sustained: although the true airspeed (tas) at an altitude is typically greater than indicated airspeed (ias), the differe
Aerodynamics Altitudes_in_aviation