On 10 May 1977, an Israeli Air Force Sikorsky CH-53 Yas'ur helicopter crashed during an exercise in the Jordan Valley, killing all 54 on board (including the 10-member flight crew). The disaster became known as Ason HaNun-Daled, or "Disaster of the 54".

It is still the worst single-aircraft accident in Israel. The crash site was in the West Bank, about 5 kilometers north of Jericho in a wadi. The cause was determined to be flying at too low an altitude during the dark, which caused the helicopter to strike a hill, crash and explode (CFIT, Controlled flight into terrain).

• 1997 Israeli helicopter disaster

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• Memorial site, in Hebrew

31°55′56″N 35°26′11″E / 31.9321°N 35.4365°E / 31.9321; 35.4365