Aerospace is the industry that designs and builds aircraft, their engines and the electronics inside them, and more and more of what these systems do is now software. Most flights inside India use one of two aircraft, the Airbus A320 or the Boeing 737. Neither is built by one company alone. Each is assembled from hundreds of thousands of parts and systems made by hundreds of suppliers.
The industry works in layers, often called tiers. At the top, the aircraft maker designs the whole aircraft, builds the body and wings, and assembles everything else into it. The jet engine makers sit beside it, and only a handful of companies make engines. Below them are the system suppliers. They make whole systems for the aircraft, such as avionics (the electronics for navigation, communication and flight control), cabins and landing gear. Parts makers supply the system suppliers. The general idea is explained under tier 1 and tier 2 suppliers.
The cabin has its own systems. The seat-back screens and their servers are in-flight entertainment. Newer aircraft are also being designed, such as the eVTOL air taxi, an electric aircraft for short hops across a city.
A supplier does not make parts for one aircraft only. A company that builds flight computers for airliners can use the same skills, and often the same testing methods, for military aircraft or for an air taxi. This is why the diagram ends by showing the same suppliers serving other aircraft.
There are two kinds of buyer. Airlines buy commercial aircraft. Governments and air forces buy military aircraft and defence electronics, and sensors such as thermal imaging cameras. Defence is tightly controlled, because countries restrict who may see a weapon's designs. So defence engineering is harder to move abroad than commercial work. Defence buyers usually buy through government tenders.
The industry moves slowly. Every new aircraft, and every change to one, must pass safety certification by aviation regulators before it may fly. A new airliner can take ten years to develop, and then it is built and flown for decades. During those decades, the maker earns again from aftermarket services, and uses data from the aircraft for predictive maintenance. The linked record of an aircraft from design to repair is called the digital thread.
Boeing and Airbus both run large engineering centres in Bengaluru.