What happens when a flight goes missing: Finding EgyptAir flight 804

The news that EgyptAir flight 804 had gone missing over the Aegean Sea on its way to Cairo Thursday was eerily familiar.

Since the disappearance of Malaysia Airlines flight 370 more than two years ago, aviation incidents have attracted increased attention. News that plane has, for example, disappeared from radar, frequently precedes confirmation of a crash and especially confirmation of the crash's cause.

EgyptAir first reported on Twitter that the Airbus A320 on its way from Paris had lost communication with radar.

Within hours, the combined resources of airlines, governments and independent aviation and marine tracking companies had reported details on the descent of the plane to 15,000 feet, the exact location where the plane was last pinpointed.

When an aircraft goes missing, dozens of independent authorities spring into action.

The state of flight tracking technology

Flight tracking technology has proliferated in the past two decades, with various satellite and radar based means opening up to amateur plane spotting networks as well as professionals. 

Popular websites such as FlightRadar24 and FlightAware offer flight tracking tools based in part on Automatic Dependent Surveillance, or ADS-B, technology. This technology allows aircraft to automatically determine its position using satellites and then broadcast, or ping, that position to ground stations. 

ADS-B is also used by other aircraft to keep track of nearby planes that could pose the threat of a mid-air collision. This technology is automatic and does not depend on pilots reporting their position.

The disappearance of Malaysian Airlines flight 370 in 2014 raised the issue of infrequent satellite reporting of a plane's position and altitude when a plane is flying beyond the reach of conventional radar and ADS-B ground stations. 

Upgrading planes to more continuous automatic reporting is underway, though not all airlines have done this throughout their fleets yet. Meanwhile, satellite-based tracking is expected to cover most of the planet by 2020.

In addition to ADS-B tracking, some airlines use systems that automatically transmit messages to their maintenance centers on the ground to log any problems. This helped investigators unravel the disappearance of Air France Flight 447, which went down off the coast of Brazil in 2009, but Malaysian Airlines did not have such a system installed on flight 370. 

If Egypt Air subscribed to such a service, it might help investigators make progress.

What happens when a flight 'disappears'

Air traffic controllers rely on radar data to track aircraft moving through their airspace. When aircraft go "missing" it usually means that they disappear from radar screens after going below a particular altitude or, in the case of an explosion, breaking up in mid-air. 

Radar data has its downsides in that it is not available over the open ocean, such as the North Atlantic, where aircraft report their positions via high frequency radio channels and use satellite-based technology during their Atlantic crossing. 

Similarly, the Indian Ocean, where Malaysian Airlines Flight 370 disappeared in 2014, does not have consistent radar coverage across the entire ocean.

In the case of the Mediterranean, radars from the many countries bordering the sea, from Spain in the northwest to Egypt in the southeast, means that the area is closely monitored. 

When an aircraft vanishes from radar screens, air traffic controllers typically alert national authorities and the airline involved to begin implementing emergency procedures. 

In the U.S., this would involve contacting the Federal Aviation Administration (FAA) as well as other federal, state and local search and rescue authorities, depending where the incident took place.

In the the case of EgyptAir Flight 804, this has caused three governments to become involved: Egypt, where the plane was headed and the airline is based; France, where the flight originated; and Greece, where the plane had just flown over before entering Egyptian airspace. 

How a water search works

Initially, when a plane disappears from radar over water, ships and aircraft are dispatched to try to locate wreckage and any survivors of a crash.

These ships do not need to be specialized search and rescue vessels with deep sea submersibles aboard. Any ships in the area of a plane crash typically respond to the call for a search and rescue operation.

The hunt for the plane's so-called "black boxes" will come next if it is determined that a plane likely went down in a particular location, with a depth that requires specialized technologies to identify and recover the flight data recorder and cockpit voice recorder. The black boxes — which are actually orange in color — contain valuable information about the moments aboard the flight before, and during, a disastrous plunge into the sea.

According to Walter Smith, a geophysicist at the National Oceanic and Atmospheric Administration (NOAA) in Maryland, if Egypt Air flight 804 "crashed somewhere along a line between Karpathos and Cairo, the deepest point in that area is about 3,000 meters deep," or about 9,800 feet.

"If the search area is as far south as has recently been reported, then it may lie on fairly smooth seafloor," Smith said in an email to Mashable.

That depth, Smith said, should be within the operational capacity of remotely operated vehicles, or ROVs, to scour the seafloor for any debris and locate the black boxes.

Smith provided more details on the seafloor topography that recovery workers may have to contend with: 

Working our way south from Karpathos to Cairo, the sea floor is initially rather mountainous, with an area called the Cretan-Rhodes Ridge. This stops at a fault in the seafloor where the African Plate is pushing under the European Plate. South of that point there is a relatively flat basin about 3000 m deep called the Herodotus Basin. Farther south, the seafloor slopes gently up toward the coast of Egypt, on the Nile Fan, an underwater river delta of sediments shed by the Nile River.

The ongoing hunt for Malaysian Airlines Flight 370 and the two-year search for Air France Flight 447, which crashed off the coast of Brazil in 2009, has led to advances in technologies used to locate aircraft wreckage as well as the all-important flight data and cockpit voice recorders.
