According to this article on aerospace-technology.com, many of the larger business jets seem to have a service ceiling of 51,000 feet. Other sources verify this trend.
What is the reason for this, if anything specific can be named? Some possibilities that I came up with are:
- engineering considerations (limitations of materials, pressurization, systems capabilities etc.)
- safety, i.e. time of usefull consciousness getting too short higher up (being less than 10 s @ 50,000ft)
- too little to be gained going higher (no congestion anymore at that alt anyway)
- an industry agreement (based on any of previous and/or other factors), in the same manner as european automakers' pact to limit the max speed of cars to 250km/h (excluding some model)
- regulatory factors
Other common "steps" appear to be 45,000 ft and 41,000, with smaller models. Nice round numbers all, but surely there has to be some reason for the magical 51,000 ft figure. Interestingly, the Learjet 85 was designed to have a service ceiling of "only" 49,000 ft, and the program got cancelled at least partially due to poor sales. It seems it was simply lacking the last 2000 ft...
Examples of business jets with 51000ft service ceiling:
Cessna Citation X