On 24 January 1963 a United States Air Force Boeing B-52C Stratofortress with nine crew members on board lost its vertical stabilizer due to buffeting stresses during turbulence at low altitude and crashed on Elephant Mountain in Piscataquis County, Maine, United States, six miles (9.7 km) from Greenville.

[2] The crew's training mission was called a Terrain Avoidance Flight to practice techniques to penetrate Advanced Capability Radar (ACR) undetected by Soviet air defense during the Cold War.

They were supposed to begin their low-level simulated penetration of enemy airspace just south of Princeton, Maine, near West Grand Lake.

After crossing Traveler Mountain, the aircraft was supposed to climb back to altitude over the Houlton VOR Station.

[2] One hour later, around 2:30 p.m. the Stratofortress crossed the Princeton VOR, descended to 500 feet (150 m) and started its simulation of penetrating enemy airspace at low altitude with an airspeed of 280 knots (520 km/h; 320 mph).

[2][4] A grader operator on a remote woods road witnessed the final turn of the Stratofortress and saw a black smoke cloud after impact.

[3] After the crash site was located the next day, Scott Paper Company dispatched plows from Greenville to clear 10 miles (16 km) of road of snow drifts up to 15 feet (4.6 m) deep.

When the US intelligence realized that the Soviets had implemented a sophisticated, layered and interconnected air defense system with radar controlled surface-to-air missiles (SAMs), the US Air Force decided the B-52 would have to penetrate the Soviet airspace at low altitude (around 500 feet or 150 metres) and high speed to stay underneath the radar.

However, low altitude, high speed flight operations put enormous stress on an aircraft's structure, especially when flying near mountains, up and down ridges and through valleys due to lee waves and the rotor.

56-0591, a B-52D, took off from Larson AFB, Washington, on 23 June 1959 and experienced a horizontal stabilizer turbulence-induced failure at low level and crashed.

[2][5] Of the two survivors, the pilot returned to active duty after spending three months in the hospital[4] and the navigator, whose feet were frostbitten, contracted double pneumonia, became unconscious for five days and his leg had to be amputated because frostbite and gangrene had set in.

[3][4] Although the site has signs posted asking viewers to show due respect while there, it has been vandalized with names carved in the wreckage or marked with permanent marker.

There is a color guard, the laying of a wreath, the reading of the names of those who died, a prayer by a military chaplain and the playing of Taps.

[4] In 2011, a Maine Forest Service employee found an ejection seat from the aircraft near an overgrown logging road while hunting.