Note: this document addresses people that are not aviation experts and uses layman’s terminology.

autorouter provides a live flight tracking functionality that people on the ground can use to following the progress of a flight and get information about departure and expected arrival.

What you see on the screen

On the left side, some basic information about the flight is displayed.

In this case the aircraft has departed and the departure time is given. In aviation, all times are given in Greenwich Mean Time (also called UTC — universally coordinated time). To make things easier, we also show the local time which is local time according to how your system is configured. In the above example the flight goes from Sweden to the UK and the browser showing the page is in the same timezone as Sweden (UTC + 2 hours). This means that the estimated arrival time of 11:18 UTC would actually be 12:18 local at the destination in England.

The information on the page updates automatically, do not have to reload the page. Normally it should update every 30 seconds which is illustrated by a counter.

Next to the flight information, we show you a map that has the planned route as a thick magenta/blue-magenta/green line and next to it the radar updates as black triangles connected with black dotted lines.

The airports are marked with their 4 letter code and an arrow pointing up for the airport of departure and an arrow pointing down for the airport of arrival.

Each black triangle is a radar update and if you move your mouse or finger over it, you get additional information.

Looking at the position report above, here’s what the fields mean:

• Position Report #10
  This is the 10th position report we received. From this you can see which direction it is going.
• Time 2015-07-29 07:12 UTC
  The time the position report was generation, i.e. the time the aircraft was overhead that position.
• GS: 132 kt
  The ground speed at the time in knots (100 knots are 182 kp/h). This is affected by the wind and whether the aircraft is climbing or descending.
• Track: 356°
  The compass direction of the movement over ground.
• Altitude: FL080
  The altitude of the aircraft in flight levels. To convert it to feet, you have to multiply the number by 100 and to convert feet to meters you have to divide it by 3.28. FL080 means 8000 feet and 2400 meters.
• Squawk: 5751
  This is a code assigned to the aircraft by air traffic control so they can easily identify it on the radar. It has no further meaning other than there are a few special squawk codes:
  • 7500: the aircraft is being hijacked
  • 7600: the aircraft has lost radio contact
  • 7700: the aircraft has a serious problem (mayday)

Limitations

The tracking makes use of radar data that is made available by air traffic controllers. There are some important limitations that users of the feature should be aware of.

When there is no tracking information

The position updates are made available by air traffic control at an interval of usually once every minute to once every 10 minutes. The interval can change during the flight and sometimes an update can go missing so there can be a considerable gap between two reports.

Data is only made available while the airplane is under control of air traffic control. Often, there are phases in the flight where the pilot navigates by himself (i.e. is not told by air traffic control where to steer to) and during these periods, there are typically no tracking updates. The prime example is when departing from or flying to an airport that is only equipped for visual flights (called “VFR”). On the planned route these segments are drawn in green color but a pilot may choose at any time to continue according to visual flight rules even when not planned from the beginning. This could mean tracking is lost.

Arrival considerations

When we show you a black triangle, we know for sure the aircraft has been at that position at the given time. However, very often we do not get timely information about landings and following our principle of only showing what we know for sure, we do not indicate a landing. It is very typical for an airport to not inform the central computer in Brussels about the landing.

You would then see the aircraft “stuck” close to the airport and the status most likely set to “arriving”. We do show you the estimated arrival time which takes all shortcuts, deviations, wind etc. encountered enroute into consideration so in almost all cases that will coincide with the actual landing time. So don’t get nervous when the aircraft is not shown as landed, we could tell you that it did but we would just be guessing which we don’t like to do.