I used to telecommute weekly from Madrid to London and back. Flying into London from Monday to Thursday became part of my lifestyle for a long time.
The itinerary Madrid (Terminal 1) to London Gatwick (South Terminal) and viceversa was part of my routine to the point that I knew the codes of my flights by heart.
During the first flights Gatwick-Barajas I realised that the airplanes consistently flew over the same landmarks: isle of Wight in England, across Bretagne in France and over Santander in Spain.
I wondered if that meant that there are “air corridors” or airways in the sky that flights with the same code followed consistently.
In order to validate this hypothesis I started to track the path of the flights with a GPS tracker.
GPS tracking during the flights
The GPS tracking device of choice was my smartphone. I switched off my smartphone at take-off and at landing times because it was mandatory by the airline.
I switched on my smartphone when the signals in the cabin allowed the passengers to do so. The GPS signal is compatible with the airplane mode because GPS tracking does not transmit radio waves. The smartphone only receives GPS data and does send anything back to the satellites.
I recorded the coordinates of most of the duration of 6 flights in the interval of 24 days from mid February to mid March. The direction of the flights were 4 flights from Gatwick to Barajas and 2 flights from Barajas to Gatwick.
I learned a few things that I am listing here:
The fixing of satellites takes much longer than on the ground
Unpredictable GPS tracking
The GPS tracking is not complete or not happening at all in some flights. Does it depended on the fuselage of the airplane or are GPS jammering devices increasingly common in commercial flights?
In some instances I might not get coordinates for hundreds of kilometers, for instance from Castille inland to the middle of the Bay of Biscay.
Similar paths on same airways
The airways were similar but not identical between flights on the same route even if separated by only 7 or 14 days.
The airways were close by a few kilometers and degrees.
Landmarks of the flights Gatwick-Barajas
Gernsey and Santander and, exceptionally Gernsey-Gijón-León.
Landmarks of the flights Barajas-Gatwick
Bilbao and Jersey.
Unreliable elevation values
The values of the elevation are zero for 50% or more of the total points of a track. Where not zero, the values were 900-1100 meters with a maximum of 1500 meters. The values that I saw displayed on the screens for passengers were 10500 meters however.
I used GpsPrune v. 18.5 by Activity Workshop to display the coordinates and maps from a .gpx export of the GPS file. GpsPrune is a program for loading, displaying and editing data from GPS receivers.