These days pilots primarily navigate through the sky using the same technology that you use on your mobile phone – GPS. The US owned Global Positioning System provides accurate position, altitude and speed information that aircraft can use to navigate around the world no matter where they are. It has become the standard in aircraft navigation due to its accuracy and reliability.
Using a system of 31 satellites in orbit twelve and a half thousand miles above the earth, GPS works by sending time-stamped signals to a receiver (similar to the ones in your phone) which then can triangulate its position using multiple signals from 3 or more satellites. With 4 satellites in view, altitude can also be calculated. This information can be constantly interpreted by the systems on board the aircraft giving the pilots up-to-date position, altitude and groundspeed data.
Even though GPS is now widely used as the primary source of navigation data for airliners, they do still use other sources such as:
Inertial Navigation System (INS)
Prior to GPS, INS would have been the main system used for navigation and is still found in new aircraft today as a back up to GPS. INS works using a system of gyroscopes and accelerometers whereby the known location of the aircraft is inputted by the crew into the system before the flight and it then measures the aircraft’s movement through space. It is generally quite accurate but can become error prone on longer flights.
Ground Based Radio Beacons
Still widely used to facilitate landing procedures at airports (and by smaller aircraft to navigate along airways), ground based beacons such as NDB’s (Non-Directional Beacons) and VOR’s (VHF Omnidirectional Range) provide direction and distance information from them to the aircraft. Their range is limited but by using multiple beacons, aircraft can easily navigate entire flights across land and short water crossings.
No longer used today but this used to be one way that pilots would navigate at night. Next time you’re in an airport keep an eye out for any aircraft with two small windows above the main cockpit windows. These are called “eyebrow” windows which allowed pilots a view of the night sky for navigation purposes and they can still be seen in some aircraft today.