An international effort is underway to locate the black boxes and wreckage of doomed EgyptAir Flight MS804, which plunged into the Mediterranean Sea on Thursday carrying 66 people. Planes, ships and submarines are now scouring the waters for a signal and debris from the crash.
As in the search for the missing Malaysian Airlines Flight MH370, which continues more than two years on, finding underwater wreckage is extremely difficult. Searchers have only a brief time frame and a small radius in which they can receive signals from an airliner's black boxes before batteries run out on the emitting devices.
While ships searching the area where EgyptAir is believed to have crashed have found some wreckage and human remains in the past few days, the black boxes, which could offer insight on the cause of the crash, were missing.
Here's what to know about the search:
Where Are Searchers Looking?
The last known location of the plane was in the Mediterranean Sea, near the Greek island of Karpathos. Search vehicles have headed to the area south of the island, which is about 180 miles north of Alexandria on the Egyptian coast, The Guardian reports. A 900 square-mile search area was set on Saturday.
The depth of the water where the search is taking place is an additional complication. The area includes one of the deepest areas in the Mediterranean, with depths as great as 1.9 miles.
What's Being Used To Find The Plane?
Egypt is taking the lead in the search effort for Flight MS804, but is coordinating with teams from France, Britain, the United States and Greece. The nations have contributed vessels and armed forces.
The U.S. Navy's 6th Feet has combed the search area with P-3 Orion aircraft, normally used for maritime surveillance. As of Sunday, the aircraft found more than 100 pieces of debris from the EgyptAir crash. The British Navy and Royal Air Force forces also have been sent to the search area, providing a supply ship and C-130 Hercules aircraft.
Greece has a submarine searching for signals from the flight recorders, as well as C-130 aircraft, The Financial Times reports.
Egypt is using a robot submarine that can reach depths of 1.9 miles. The probe is usually used to monitor offshore oil rigs. On Wednesday, EgyptAir chairman Safwat Musallam announced that two firms from France and Italy had been contracted to aid in the search. The unnamed companies have the ability to search to depths of 3,000 feet, Reuters reports Musallam saying.
How Long Will It Take To Find?
It's unclear. The international search teams face a number of hurdles. Batteries that power signals from the airliner's black boxes will likely be exhausted in less than 30 days. If the boxes aren't located before that happens, searchers must switch to using sonar devices in a process that will take even longer. Even while signals from the black boxes are operational, the pings may not have enough range to reach the surface if they are 1.9 miles deep. In that case, underwater options, such as submarines or submerged listening devices, may be necessary to find the signal, according to Reuters.
On Monday, Egypt's Civil Aviation Minister Sherif Fathy told NBC News that searchers were "far away" from finding the plane's fuselage.
Authorities are anxious to determine what caused the crash. Officials have oscillated between suggesting the possibility of a terror attack, and cautioning against jumping to any conclusions based on the limited data and evidence collected. Egypt's Fathy said on Monday that finding the black boxes would be key to understanding the circumstances that brought down the aircraft.
This post has been updated to include information on two firms hired by EgyptAir to aid in the search.