Aircraft manufacturing is the business of designing a whole aircraft, building its body and wings, fitting every supplier's system into it, and getting it certified before it may fly. The companies that do this are called aircraft makers, airframers or, in defence, prime contractors.
An aircraft maker does not make everything itself. The airframe is the body and wings, and the maker builds that. The engines come from engine makers. The electronics for navigation, communication and flight control, called avionics, come from system suppliers. The cabin, landing gear and large parts of the airframe come from other suppliers. These suppliers in turn buy from smaller makers, as explained under tier 1 and tier 2 suppliers.
Say a maker is building a narrow-body airliner for an Indian airline. Its engineers keep the design of every part in product lifecycle management (PLM) software, together with a record of who approved each change. Suppliers deliver their systems to the assembly line. The maker fits the wings, the engines and the electronics, and then runs ground tests and test flights. A regulator then certifies that the aircraft is safe, under safety certification rules. Only after that does the maker hand the aircraft over to the airline.
The airline pays the maker in stages. It usually pays a deposit when it places the order. It then makes further payments while the aircraft is being built, and pays the balance when the aircraft is delivered. The maker spends years and a very large amount of money before the first delivery. So it needs orders for many aircraft before it starts, and it earns back the cost over the decades in which the type is built and serviced.
The maker's hardest data problem is that designs, parts lists and test results sit in dozens of separate systems. Engineering data integration joins them. The linked record is called the digital thread. Suppliers must also log in to the maker's systems to share designs. For defence aircraft, those logins are recorded and limited by vendor privileged access management.
The two largest makers of airliners are Boeing and Airbus. Both run large engineering centres in Bengaluru.