Roald Amundsen, the famous Norwegian Arctic explorer, died in 1928 while attempting to rescue his fellow Arctic explorer, Italian Umberto Nobile. He took off with several other crew in a French-built and -crewed Latham 47 flying-boat, which disappeared over the sea.
According to the Search For Amundsen Web site:
On June 18th, 1928 Amundsen and the French team members left for the rescue of the Italia crew. At about 4 p.m. they took off from Tromsø, Norway.
None of the transmissions mentioned technical difficulties, which implied that the flight was progressing as planned. However, the transmission did reveal difficulties with the radio. In the late 1920s, this was quite common. It is assumed that the accident took place somewhere in the area around Bear Island. Between 6.45 and 6.55 p.m., the last radio call was sent from Latham 47 and from that point on the connection fell silent forever.
There have been several discoveries over the years of pieces of wreckage presumed to come from the aircraft. However, the aircraft itself has never been located. The search is now being renewed, using modern side-scanning sonar and remotely-operated submersibles. According to the Search For Amundsen Web site:
[At the] end of August, the team and ships will leave Tromsø for a mission that will keep them at sea for almost two weeks, searching an area of 45 square miles. Two ships will work together: KNM Tyr, a Royal Norwegian Navy Vessel, and its supply vessel, the KV Harstadt, belonging to the fleet of the Norwegian Coast Guard. Most important for the success of the mission are the high tech apparatus that will be onboard.
Two remotely operated submersibles will be used during the search. Modern sonar can capture images of startling clarity, even at great depths. The pictures below are of an aircraft and a ship on the sea-bed in the search area (the former probably a casualty of World War II, when many aircraft were lost during convoy battles, etc. The elliptical wings on this aircraft suggest it's the remains of a German Heinkel He 111 bomber - compare them to the photographs at the link.)
Will the search finally discover the last resting-place of Norway's greatest explorer? Only time will tell. Good luck to all involved.