When Malaysian Airlines MH370 vanished in March this year the call went up for better tracking technology to be installed on all passenger aircrafts.
Many people asked how, in an age of global connectivity and satellite communications and positioning systems, an aircraft with 239 people on board could simply disappear.
Now, with crash of another aircraft, those calls have been renewed.
These are some of the available aircraft tracking technology:
It is not immediately clear what tracking devices are on board the missing Airbus A320-200 but it is almost certain to have been carrying a transponder – an electronic device that responds when it receives a radio signal.
It helps identify the aircraft on air traffic control radar systems, giving out the plane’s location and its altitude, and makes it possible to detect if the aircraft is at risk of colliding with another. When flight QZ8501 “disappeared from radar” early on Sunday morning it was because this transponder system stopped transmitting for some reason.
Air traffic controllers can also try to make verbal contact with the aircraft using a high-frequency radio system. No mayday call was made by the pilot of flight QZ8501, but the system is one way a pilot in trouble can raise the alarm.
“There’s really nothing the people on the ground can do,” says Keith Mackey, an expert on aviation safety and over 30 years’ experience as a pilot.
“Pilots have to take care of the situations themselves and other than advising the ground what is going on there is no way that the ground is really going to be able to help.”
Passenger aircraft also carry emergency transmitters beacons. These send a signal, either via satellite or on radio waves, following a crash, to help locate the aircraft. In the past these have proved most helpful when planes crash on land and within a small search area.
“They will ping for at least 30, up to 90 days, ” says Steven Wallace, the former head of Accident Investigations for the US Federal Aviation Authority.
Underwater microphones can be used when the aircraft concerned has crashed into the sea.
The missing Malaysian Airlines flight MH370 was fitted with an transponder from telecommunications company Inmarsat. This allowed the planes location to be tracked via satellite even after the radar transponder was switched off. Inmarsat says the missing AirAsia flight was not outfitted with its tracking technology.
Most new planes are now fitted with an ACARS (Aircraft Communication Addressing and Reporting System). This system, which uses radio or satellite links, automatically sends data such as height, speed and engine performance to engineering teams at the airline. The aircraft in question entered service with AirAsia in 2008. It is not clear if such a system was installed.
Since MH370 vanished earlier this year a number of different advanced tracking systems have been proposed for passenger aircraft. But getting universal agreement on the most efficient and effective of these, and then installing the system on tens of thousands of aircraft is expected to take years.
Follow Tarek Bazley on Twitter: @tarekbazley