Zoning of large aircraft is specified by the Air Transport Association of America in the ATA-100 Specification.
A zone is identified by one of three indicators, depending upon whether it is a major zone, major sub-zone, or simply a zone.
Major zones are identified by three digit numbers as follows:
Major Zone Area
100 Lower half of the fuselage to the rear pressure bulkhead (below the main cabin deck).
200 Upper half of the fuselage to the rear pressure bulkhead.
300 Empennage, including fuselage aft of the rear pressure bulkhead.
400 Power plants and struts or pylons.
500 Left wing.
600 Right wing.
700 Landing gear and landing gear doors.
900 Reserved for uncommon differences between aircraft types not covered by standard series numbers.
The standard series is from 100 to 800 and the special series numbers are in the 900 bracket.