Because that is just less than the highest altitude they have been tested at.
The service ceiling of an aircraft is the maximum altitude that the aircraft can safely maintain.
Budapest Aircraft Service was created in 1991.
The pipes are on the outside of the walls and ceilings. It's much easier to service.
The Airbus A380 is the largest passenger aircraft.
Pyramid Peak Aircraft Warning Service Lookout was created in 1942.
Aircraft service and maintenance is done in a Hangar. It is the resting place for a plane. It can also be done in an open field.
You are propably looking for the Concorde or the Tupolev Tu-14. It should be noted, however, that none of these aircraft are in service today. Further, there are currently no supersonic aircraft in commercial service.
You need to be specific with this, which aircraft, which variant of the aircraft, right down to which engines are fitted, what load you are carrying etc etc etc Any change to this data will change the service ceiling.
As of 23/10/2015, Air China has 340 aircraft in service.
The relevant service manual for that aircraft.
13,400 feet
It contains all the necessary information for an aircraft engineer to trouble shoot,service,functionally and repair all the system in an aircraft.