A flight engineer is a member of an airplane crew who is responsible for overseeing the systems on an airplane during flight to confirm that they are working and to enact repairs or corrections if necessary. Flight engineers are increasingly being replaced by computerized systems which serve the same functions, but they are still necessary on some aircraft. The military is a major employer of flight engineers, and many flight engineers enjoy military work because they get to explore cutting edge aircraft and to work in very diverse conditions.

Before an aircraft takes off, a flight engineer inspects it to confirm that it is safe to fly and to run down the preflight checklist. Once a plane is in flight, the flight engineer monitors all of the plane's systems for signs of problems, and controls engine power, the electrical systems, fuel usage, pressurization, air conditioning, and air in the cabin of the aircraft. Flight engineers work with the pilot to address the pilot's needs, and they are also prepared to address unexpected events while in flight. After the flight, the plane is inspected again.

Flight engineers have training in airplane mechanics and the various tasks they will need to perform. They must also usually be licensed by a regulatory agency, usually the same agency which licenses pilots. Flight engineers have to demonstrate time spent in the classroom and time spent gathering practical skills working on aircraft to be certified, and they also usually need to pass an exam to become certified. In addition, they may need to pass a medical exam to confirm that they are safe to fly.

Some flight engineers are also pilots. Historically, the flight engineer could potentially step in to pilot the plane if a problem developed, and modern flight engineer-pilots tend to keep up their licenses to confirm that they are capable of flying a plane if necessary. On some airlines, the flight engineer is known as the second officer, and working as a second officer is the first step in climbing the career ladder to become an airline pilot.

In addition to working on operational aircraft, flight engineers can also be involved in aviation research and development. Their practical skills can be applied to troubleshooting experimental aircraft, developing new systems for aircraft, and testing aircraft as they move through the various design phases. To obtain this kind of work, a flight engineer generally needs to have extensive education and experience, and a pilot's license is often strongly recommended.