Flight instruments are specifically referred to as those instruments located in the cockpit of an aircraft that provide the pilot with the information about the flight situation of the aircraft, such as position, speed, and attitude. The flight instruments are of particular use in conditions of poor visibility, such as in clouds, when such information is not available from visual reference outside the aircraft. The term is sometimes used loosely as a synonym for cockpit instruments as a whole, in which context it can include engine instruments, navigational instruments, and communication equipment.
Historically, the first instruments needed on board were the magnetic compass and a clock in order to calculate directions of flight and times of flight. To calculate the remaining fuel in the tanks, a glass pipe showing the level of fuel was presented on the cockpit. Before World War I, cockpits begin to present altimeters, anemometers, tachometers, etc. In the period between wars (1919-1939), the era of the pioneers, more and more sophisticated instruments were demanded to fulfill longer and longer trips: the directional gyro (heading indicator) and the artificial horizon (attitude indicator) appeared, and the panel of instruments started to have a standard layout.
Nowadays, in the era of electronics and information technologies, the cockpits present the information in on-board computers, using digital indicators and computerized elements of measure. Since instruments play a major role in controlling the aircraft and performing safe operations in compliance with air navigation requirements, it is necessary to present data in a clean and standard layout, so that the pilot can interpret them rapidly and clearly. The design of on board instruments requires knowing the physical variables one wants to measure, and the concepts and principles within each instrument.