Aircrew, also called flight crew, are personnel who operate an aircraft while in flight. The composition of a flight’s crew depends on the type of aircraft, plus the flight’s duration and purpose.

Flying personnel include, for example (delimitation in JAR-FCL ):

Pilot (flight crew)
Flight attendant (cabin crew)
Purser (cabin crew)
Ground personnel include, for example:

technical staff such. In the field of aircraft maintenance (eg aircraft mechanics )
Flight dispatcher
The training and licensing of aviation personnel is governed by the Aviation Personnel Regulation. In Germany, the Federal Aviation Authority is responsible for aviation personnel, which checks the requirements and capabilities of aviation personnel and licenses. In addition, there are many training and professional regulations for almost every aviation profession.

Flying Staff
The flying staff is part of an airline’s workforce and essentially works on board aircraft. It is part of the aviation staff and consists of different occupations or functionaries:

Responsible pilot : official name in the pilot license: “commercial pilot” or “professional pilot”; Function name: “Captain of the Flight”, also “Commander”
First officer : legal German designation: “second pilot”, also: “copilot”, “copilot”, “first officer”
Flight engineer (only in some, mostly older types )
flight attendant
In military aviation, among other weapons system officer, navigator, loadmaster, observer, gunner, on-board radio
As is the case with ground crew (if in contact with the public), flying personnel usually wear work clothes (uniform).

Commercial aviation

Flight deck positions
In commercial aviation, the aircrew are called flight crew. Some flight crew position names are derived from nautical terms and indicate a rank or command structure similar to that on ocean-going vessels, allowing for quick executive decision making during normal operations or emergency situations. Historical flightdeck positions include:

Captain, the pilot designated as the Pilot-In-Command (PIC), and the highest-ranking member or members of a flight crew.
First Officer (FO, also called a co-pilot), another pilot who is not the pilot-in-command, and is normally seated to the right of the captain. (On helicopters, an FO is normally seated to the left of the captain, who occupies the right hand seat).
Second Officer (SO), a person lower in rank to the First Officer, and who typically performs selected duties and also acts as a relief pilot. The rank of Second Officer was traditionally a Flight Engineer, who was often the person who handled the engine controls. In the 21st century, second officers on some airlines are pilots who act as “cruise relief” on long haul flights.
Third Officer (TO), a person lower in rank to a Second Officer, and who typically performs selected duties and can also act as a relief pilot. Largely redundant in the present day.
‘Relief Crew’ members in the present day are fully licensed and trained Captains and First Officers who accompany long-haul airline flights, and who relieve the primary pilots during designated portions of the flight to provide them with rest or sleep breaks (some large wide-body airliners are equipped with special pilot sleeper berths, but more typically reserved seats in the section closest to the flight deck, or cockpit, are used for the relief crew). The number of relief crew members assigned to a flight depends in part on the length of the flight and the official air regulations the airline operates under.
Flight Engineer (FE), a position originally called an ‘Air Mechanic’. On older aircraft, typically between the late-1920s and the 1970s, the Flight Engineer was the crew member responsible for engines, systems and fuel management. As aircraft became increasingly sophisticated and automated, this function has been mostly assumed by the primary pilots (Captain and FO), resulting in a continued downsizing in the number of aircrew positions on commercial flights. The Flight Engineer’s position is commonly staffed as a Second Officer. Flight engineers can still be found in the present day (in greatly diminished numbers), used on airline or air freight operations still flying such older aircraft. The position is typically crewed by a dual-licensed Pilot-Flight Engineer in the present day.
Airborne Sensor Operator, An airborne sensor operator (aerial sensor operator, ASO, Aerial Remote Sensing Data Acquisition Specialist, Aerial Payload Operator, Police Tactical Flight Officer, Tactical Coordinator etc.) is the functional profession of gathering information from an airborne platform (Manned or Unmanned) and/or oversee mission management systems for academic, commercial, public safety or military remote sensing purposes. The airborne sensor operator is considered a principal flight crew or aircrew member.
Navigator (archaic), also called ‘Air Navigators’ or ‘Flight Navigators’. A position on older aircraft, typically between the late-1910s and the 1970s, where separate crew members (sometimes two navigation crew members) were often responsible for the flight navigation, including its dead reckoning and celestial navigation, especially when flown over oceans or other featureless areas where radio navigation aids were not originally available. As sophisticated electronic air navigation aids and universal space-based GPS navigation systems came online, the dedicated Navigator’s position was discontinued and its function was assumed by dual-licensed Pilot-Navigators, and still later by the aircraft’s primary pilots (Captain and FO), resulting in a continued downsizing in the number of aircrew positions on commercial flights. Modern electronic navigation systems made the navigator redundant by the early 1980s.
Radio Operator (archaic). A position on much older aircraft, typically between the mid-1910s and the 1940s, where a separate crew member was often responsible for handling telegraphic and voice radio communications between the aircraft and ground stations. As radio sets became increasingly sophisticated and easier to operate, the function was taken over directly by a FO or SO, and still later by the pilot-in-command and co-pilot, making the radio operator’s position redundant.

Cabin positions
Aircraft cabin crew members can consist of:

Purser or In-flight Service Manager or Cabin Services Director, is responsible for the cabin crew as a team leader.
Flight attendant or Cabin Crew, is the crew member responsible for the safety of passengers. Historically during the early era of commercial aviation, the position was staffed by young ‘cabin boys’ who assisted passengers. Cabin boys were replaced by female nurses, originally called ‘stewardesses’. The medical background requirement for the flight attendant position was later dropped.
Flight medic, is a specialized paramedic employed on air ambulance aircraft or flights.
Loadmaster, is a crew member on a cargo aircraft responsible for loading freight and personnel, and for calculating the aircraft’s weight and balance prior to flight, which must be within the aircraft manufacturer’s prescribed limits, for safe flight. On non-cargo aircraft, weight and balance tasks are performed by the flight crew.

Military
From the start of military aviation, additional crew members have flown on military aircraft. Over time these duties have expanded:

Pilot
Co-pilot
Air gunner, crew member responsible for the operation of defensive weapons, for example gun turrets. Specific positions include nose gunner, door gunner and tail gunner
Bombardier or Bomb Aimer is a crew member for the release of ordnance, particularly bombs.
Boom operator, in the USAF the crew member on tanker aircraft responsible for operating the flying boom and the transfer of fuel.
Combat systems officer
Airborne Sensor Operator, An airborne sensor operator (Aerial Sensor Operator, Tactical Coordinator, EWO etc.) is the functional profession of gathering information from an airborne platform (Manned or Unmanned) and/or oversee mission management systems for tactical, operational and strategic remote sensing purposes.
Crew chief, an enlisted aircraft mechanic responsible for the maintenance and preparation of the aircraft.
Flight engineer, a crew member responsible for engines, systems and fuel management.
Flight officer
Flight surgeon, not involved in the operation of the aircraft but is considered by some militaries to be aircrew.
Loadmaster, crew member responsible for loading freight and personnel and the weight and balance of the aircraft.
Navigator, a crew member responsible for air navigation. Still actively trained and licensed in some present day militaries, as electronic navigation aids can not be assumed to be operational during warfare.
Air observer
Rescue swimmer on air-sea rescue aircraft
Signaller or radio operator, crew member responsible for the operation of the aircraft communications systems.
Tactical coordinator
Weapon systems officer or “weapon systems operator”

Aerospace and Space
For airships, the term ship’s crew is customary for the flying personnel, positions include here Navigator, Purser, flight attendants and various military personnel.

In space travel, the term ship’s crew refers to the crew aboard a manned spacecraft . In the Space Shuttle, the ship’s crew consists of a commander, a pilot, and several flight-trained mission specialists, while for the Russian Soyuz spaceships, it is composed mostly of commander and flight engineer . On a space station, the staff is called a regular crew . Since the mission Soyuz TM-3In July 1987, it is customary for the permanent crew to receive visits from guests or visiting teams docking with a spacecraft at the station. In addition, since the spaceflight of Toyohiro Akiyama in December 1990, there is the so-called space tourism . In contrast to the guests, the tourists do not belong to the staff and they are not assigned any tasks. A crew is selected from a larger group of spaceman candidates due to the high training effort generally years prior to spaceflight . Depending on the meaning of the mission Substitute people are being trained to replace a disabled astronaut shortly before take-off.

Source from Wikipedia