Prior to the advent of GNSS , '' ' Celestial Navigation ' '' was also used by trained navigators on military bombers and transport aircraft in the event of all electronic navigational aids being turned off in time of war . Originally navigators used an astrodome and regular sextant but the more streamlined periscopic sextant was used from the 1940s to the 1990s . From the 1970s airliners used inertial navigation systems , especially on inter-continental routes , until the shooting down of Korean Air Lines Flight 007 in 1983 prompted the US government to make GPS available for civilian use
Korean Air Lines Flight 007
Korean Air Lines Flight 007
Air navigation