The search for Malaysia Airlines flight MH370 is entering its fourth day.
Navy ships, military aircraft, helicopters, coastguard and civilian vessels from 10 nations have criss-crossed the seas off both coasts of Malaysia without finding a trace of the Beijing-bound Boeing 777-200ER or its 239 passengers and crew.
As the search continues, here are four other famous missing aircraft mysteries.
Air France Flight 447
A disappearance with some unnerving similarities to the Malaysia Airlines search. On June 1, 2009, without warning and on a routine transatlantic flight from Rio de Janeiro to Paris, the Airbus jetliner vanished into the ocean. It fell so quickly that its pilot had no chance to make a distress call. The victims numbered 228, including one Canadian.
It took five days of intensive international effort, and with periods of time when searchers were concerned whether they were looking in the right place, before any confirmed wreckage was recovered.
The famous millionaire adventurer departed from his Nevada ranch in 2007 to scout for locations to try to set a land-speed record. He was reported missing by a friend when he did not return. After several fruitless searches, Mr. Fossett was declared legally dead five months later on Feb. 15, 2008.
It took 13 months before the discovery of the plane wreckage. On Oct. 1st, 2008, investigators found tiny amounts of human remains and clothing at a remote crash site in Inyo National Forest, about 200 kilometres south of the Nevada ranch from where he had departed.
Less than four months after becoming a hero of the Toronto Maple Leafs' Stanley Cup win, the popular defenseman boarded a yellow 24 Fairchild pontoon plane with his fishing buddy Dr. Henry Hudson on Aug. 26, 1951, near the southern tip of James Bay. They never arrived at their destination.
A massive search involving several aircraft lasted several weeks and covered thousands of square kilometers of dense northern Ontario bush. It wasn't until almost 11 years later, in June 1962, that the wreckage was discovered by a helicopter pilot near Cochrane, Ont. The skeletal remains of both men were still strapped into their seats.
Amelia Earhart and Fred Noonan
The famous pilot and her navigator departed Papua New Guinea on July 2, 1937 in a quest to circumnavigate the globe along the equator. Although scheduled to refuel at Howland Island, which is 480 kilometres from Nikumaroro, Ms. Earhart radioed that she could not find the island and was low on fuel.
The duo disappeared that day. The United States government commenced what became the most extensive air and sea search in naval history thus far, but on July 19, after spending $4-million and covering 250,000 square miles of ocean the recovery mission was called off. To date there has been no recovery of Earhart and Noonan's remains or of their Lockheed Electra.
Sources: The Globe and Mail, The Canadian Press, Reuters, Amelia Earhart Official Website