Part 135 is actually a chapter in the FARs (Federal Aviation Regulations). It governs primarily charter and air taxi operations and sets the requirements for the people and aircraft performing on-demand and commuter operations. It comprises thirteen sections, the first being the SFARs (Special Federal Aviation Regulations), which deal with special situations, and the last section being the appendix. There are eleven subparts that are broken down and represented by the letters "A" – "K".
Part 135 mainly applies to charter and air taxi operations because it references on-demand and commuter flights. A "charter" means a contract with a person or community of people for the leased aircraft, so charter operations are always on-demand. This is the same for air taxis. The subparts are divided up and explained in the following graph:
|A||General||basic compliance of rules, drugs, and alcohol|
|B||Flight Operations||flight rules for cargo, polar regions, airworthiness, inspections, and emergencies|
|C||Aircraft and Equipment||equipment, oxygen, and instrument requirements|
|D||VFR/IFR Operating Limitations and Weather Requirements||VFR and IFR weather minimums, distance minimums, and alternate airports|
|E||Flight Crewmember Requirements||operating experience and use of drugs|
|F||Crewmember Flight Time and Duty Period Limitations and Rest Requirements||rest limitations, helicopter emergencies, and duty periods|
|G||Crewmember Testing Requirements||required testing for crewmembers|
|H||Training||required training for crewmembers|
|I||Airplane Performance Operating Limitations||limitations of large and small transport category aircraft as well as non-transport category aircraft|
|J||Maintenance, Preventative Maintenance, and Alterations||any maintenance or changes performed on the aircraft|
|K||Hazardous Materials Training program||programs for hazardous material training purposes|
Not only are charters supposed to operate under Part 135, but it benefits them to do so. Part 135 operates much like Part 121 (commercial aircraft), but it has stricter rules, giving the charter companies an advantage. One might think that having stricter rules gives a company a disadvantage, but in fact it makes the company better, faster, safer, and more reliable.