When an aircraft goes missing, investigators never rely on a single data source to reconstruct what happened. They piece together a trail from radar, transponders, ADS-B signals, satellite systems, air traffic control recordings, and the aircraft's own flight recorders.
The layered tracking process is now playing out in real time following the crash of a K2 Airways Boeing 737-400 cargo flight that went down in the Arabian Sea while flying from Sharjah to Karachi.
The plane, with its two pilots, one load master, and two engineers, had a navigation problem at 9:18 PM Pakistan time and was at a distance of about 155 nautical miles from Karachi. Air Traffic Controllers assisted the plane's crew for three minutes, but then, according to radar, it descended quickly along with a sharp turn, and then there was a complete loss of contact at 9:21 PM.
The last radio message sent by the crew said that their plane was "rolling or floating." Later on, debris was found about 53 nautical miles away from Ormara after 12 hours of searching involving the Pakistan Navy frigate "PNS Zulfiquar" and the air force surveillance planes. All five members of the crew are still missing.
Flightradar24, a flight tracking service, said ADS-B data indicated the aircraft was flying at an altitude of 35,000 feet, but it began its descent to approximately 29,475 feet and climbed up again to about 36,650 feet. Afterward, it had a very steep descent to 1,100 feet at a rate of 22,400 feet per minute.
The ADS-B is the primary technology used by most flight trackers, and it transmits an aircraft's GPS location, altitude, and speed to ground stations and other planes as recommended by the FAA.
However, it is not flawless, as coverage gets affected when flying over open water, at low altitude, or when onboard systems cease transmissions. It is important to note that Flightradar24 also indicated that the plane received GNSS interference immediately after taking off from Sharjah.
Once contact is lost, the technological challenge shifts from tracking to recovery. Saj Ahmad, chief analyst at London-based StrategicAero Research, said that locating the wreckage and searching the debris field for the flight data recorder and cockpit voice recorder will require specialist naval equipment, including submersible drones.
He added that Boeing and engine manufacturer CFM International are expected to deploy specialist teams to support the investigation, since their technical expertise will likely be critical to determining what went wrong.
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The 27-year-old airplane, with registration number AP-BOI, has been previously used by Aeroflot, Garuda Indonesia, and FedEx operators before becoming a cargo aircraft and finally landing at K2 Airways in 2024, which allegedly is the sole working aircraft at K2 Airways. Ahmad emphasized that K2 would also have to go through the aircraft's maintenance records to identify any possible oversight during maintenance, although investigators do not mention any link between maintenance and the accident.
As Pakistan's aviation regulatory body still has not provided its preliminary results of the accident, officials urge against any conclusions due to public speculations based on the tracking data.