Wreckage of Pan Am plane that shaped aviation safety found 74 years on

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Watch: Moment research team gets first look at Pan Am plane wreckage after 74 years

The wreckage of a Pan American Airways plane has been found 74 years after it plunged into the Atlantic Ocean in a crash that prompted mandatory airline safety briefings.

The Clipper Endeavor was found 2,000ft (610m) below sea level off the coast of Puerto Rico with a sonar-equipped drone. It went down on 11 April 1952 following multiple-engine failure shortly after take-off.

Everyone onboard survived the impact - but passengers struggled to locate life vests and rafts as the plane rapidly sank. Of the 69 passengers and crew onboard, just 17 survived.

The disaster led to sweeping reforms in aviation safety, including compulsory pre-flight safety briefings on every commercial flight.

Image source, Air/Sea Heritage Foundation and Deep Sea Vision Image caption, Wreckage of the Clipper Endeavour was discovered more than seven decades after the aircraft disappeared

The expedition to find the wreckage was led by the Air/Sea Heritage Foundation in partnership with the Discovery Channel's Expedition Unknown show and several other organisations.

Last month, explorers discovered the ruins of the Douglas DC-4 aircraft using an autonomous sonar drone that detected the aircraft's fuselage and tail.

"We are all stunned and elated ​by this ​discovery, yet also humbled ⁠to remember what happened in that place so long ago," said Russ Matthews, president of ​the Air/Sea Heritage Foundation.

The plane had been carrying 64 passengers and five crew to New York when the pilot was forced to make a violent water landing.

The confusion that ensued became a "catalyst" for modern regulations mandating better flotation equipment on planes and preflight briefings on how to use it, aviation safety expert John Cox told AP.

Image source, Pan Am Historical Foundation Image caption, The Clipper Endeavor sank minutes after a hard water landing, killing 52

Today, before every commercial flight, cabin crew are required to outline where a plane's exits are, as well as the location of life vests and how to inflate them.