1956 Grand Canyon mid-air collision

The airspace over the canyon was not under any type of radar observation and there were no homing beacons or "black boxes" (cockpit voice and flight data recorders) aboard either aircraft. The last position reports received from the flights did not reflect their locations at the time of the collision. Also, there were no credible witnesses to the collision itself or the subsequent crashes.

The only immediate indication of trouble was when United company radio operators in Salt Lake City and San Francisco heard a garbled transmission from Flight 718, the last from either aircraft. Civil Aeronautics Board (CAB) accident investigation engineers later deciphered the transmission – which had been preserved on magnetic tape – as the voice of co-pilot Robert Harms declaring, "Salt Lake, [ah], 718 ... we are going in!" The shrill voice of Captain Shirley was heard in the background as, presumably futilely struggling with the controls, he implored the airplane to "[Pull] up! [Pull] up!" (bracketed words were inferred by investigators from the context and circumstances in which they were uttered).[11]

After neither flight reported their current position for some time, the two aircraft were declared to be missing, and search and rescue procedures started. The wreckage was first seen late in the day near the confluence of the Colorado and Little Colorado Rivers by Henry and Palen Hudgin, two brothers who operated Grand Canyon Airlines, a small air taxi service.[12] During a trip earlier in the day, Palen had noted dense black smoke rising near Temple Butte, the crash site of the Constellation, but had dismissed it as brush set ablaze by lightning.

Burial site and memorial for the TWA passengers and crew, Citizens Cemetery, Flagstaff, Arizona. 1956 funeral photo from Life magazine.

However, upon hearing of the missing airliners, Palen decided that what he had seen might have been smoke from a post-crash fire. He and his brother flew a light aircraft (a Piper Tri-Pacer) deep into the canyon and searched near the location of the smoke. The Constellation's empennage was found, and the brothers reported their findings to authorities. The following day, the two men pinpointed the wreckage of the DC-7. Numerous helicopter missions were subsequently flown down to the crash sites to find and attempt to identify victims, as well as recover wreckage for accident analysis, a difficult and dangerous process due to the rugged terrain and unpredictable air currents.[13]

Close-up of plaque honoring TWA passengers and crew, Citizens Cemetery

The airlines hired the Swiss Air-Rescue[14] and some Swiss mountain climbers to go to the scene where the aircraft fuselages had crashed. They were to gather the remains of the passengers and their personal effects. This was given considerable publicity in U.S. news releases at the time because of the ruggedness of the terrain where the fuselages came to rest.

Owing to the great violence of the impacts, no bodies were recovered intact and positive identification of most of the remains was not possible. On July 9, 1956, a mass funeral for the victims of TWA Flight 2 was held at the canyon's south rim.[15] Twenty-nine unidentified victims of the United flight were interred in four coffins at the Grand Canyon Pioneer Cemetery. Sixty-six of the seventy TWA passengers and crew are buried in a mass grave at Citizens Cemetery in Flagstaff, Arizona. A number of years elapsed following this accident before most of the wreckage was removed from the canyon. Some pieces of the aircraft remain at the crash sites.

The investigation of this accident was particularly challenging due to the remoteness and topography of the crash sites, as well as the extent of the destruction of the two airliners and the lack of real-time flight data as might be derived from a modern flight data recorder. Despite the considerable difficulties, CAB experts were able to determine with a remarkable degree of certainty what had transpired and, in their report, issued the following statement as probable cause for the accident:[16]

The Board determines that the probable cause of this mid-air collision was that the pilots did not see each other in time to avoid the collision. It is not possible to determine why the pilots did not see each other, but the evidence suggests that it resulted from any one or a combination of the following factors: Intervening clouds reducing time for visual separation, visual limitations due to cockpit visibility, and preoccupation with normal cockpit duties, preoccupation with matters unrelated to cockpit duties such as attempting to provide the passengers with a more scenic view of the Grand Canyon area, physiological limits to human vision reducing the time opportunity to see and avoid the other aircraft, or insufficiency of en route air traffic advisory information due to inadequacy of facilities and lack of personnel in air traffic control.

In the report, weather and the airworthiness of the two planes were thought to have played no role in the accident. Lacking credible eyewitnesses and with some uncertainty regarding high altitude visibility at the time of the collision, it was not possible to determine conclusively how much opportunity was available for the TWA and United pilots to see and avoid each other.[16]

Neither flight crew was specifically implicated in the CAB's finding of probable cause, although the decision by TWA's Captain Gandy to cancel his IFR flight plan and fly "1,000 on top" was the likely catalyst for the accident. Also worth noting was that the investigation itself was thorough in all respects, but the final report focused on technical issues and largely ignored contributory human factors, such as why the airlines permitted their pilots to execute maneuvers solely intended to improve the passengers' view of the canyon. It would not be until the late 1970s that human factors would be as thoroughly investigated as technical matters following aerial mishaps.[12]

During the investigation, Milford "Mel" Hunter, a scientific and technical illustrator with Life magazine, was given early and unrestricted access to the CAB's data and preliminary findings, enabling him to produce an illustration of what likely occurred at the moment of the collision. Hunter's finely detailed gouache painting first appeared in Life's April 29, 1957, issue[17] and was subsequently included in David Gero's 1996 edition of Aviation Disasters II.

In a letter to Gero in 1995, Hunter wrote:[note 3]

I was able to plot the two intersecting flight paths and the fact that both planes were in each other's blind spot. I remember showing that the descending aircraft's propellers chewed a series of gashes along the fuselage top of the ascending aircraft. I did a lot of this type of factual re-creation for Life. They were always extremely tough to piece together to the satisfaction of all the editors, art directors and assorted researchers who were assigned to such projects. But, it was extremely interesting work.

Hunter's recollection of his illustration was not completely accurate. The painting showed the DC-7 below the Constellation, with the former's number one engine beneath the latter's fuselage, which agreed with the CAB technical findings.[17][18]

At 128 fatalities, the Grand Canyon collision became the deadliest U.S. commercial airline disaster and deadliest air crash on U.S. soil of any kind, surpassing United Airlines Flight 409 the year before. It was surpassed in both respects on December 16, 1960, by the 1960 New York mid-air collision (also involving United and TWA aircraft).

The accident was covered by the press worldwide, and as the story unfolded, the public learned of the primitive nature of air traffic control (ATC) and how little was being done to modernize it. The air traffic controller who had cleared TWA to "1,000 on top" was severely criticized as he had not advised Captains Gandy and Shirley about the potential for a traffic conflict following the clearance, even though he must have known of the possibility. The controller was publicly blamed for the accident by both airlines and was vilified in the press, but he was cleared of any wrongdoing. As Charles Carmody (the then-assistant ATC director) testified during the investigation, neither flight was legally under the control of ATC when they collided, as both were "off airways." The controller was not required to issue a traffic conflict advisory to either pilot. According to the CAB accident investigation final report, page 8, the en-route controller relayed a traffic advisory regarding United 718 to TWA's ground radio operator: "ATC clears TWA 2, maintain at least 1,000 on top. Advise TWA 2 his traffic is United 718, direct Durango, estimating Needles at 0957." The TWA operator testified that Captain Gandy acknowledged the information on the United flight as "traffic received."[19]

The accident was particularly alarming in that public confidence in air travel had increased during the 1950s with the introduction of new airliners like the Super Constellation, Douglas DC-7, and Boeing Stratocruiser. Travel by air had become routine for large corporations and vacationers often considered flying instead of traveling by train. At the time, a congressional committee was reviewing domestic air travel, as there was growing concern over the number of accidents. However, little progress was being made and the state of ATC at the time of the Grand Canyon accident reflected the methods of the 1930s.

As near-misses and mid-air collisions continued, the public demanded action. Often-contentious congressional hearings followed, and in 1957, increased funding was allocated to modernize ATC, hire and train more air traffic controllers, and procure much-needed radar – initially military surplus equipment.

However, control of American airspace continued to be split between the military and the Civil Aeronautics Administration (CAA, the federal agency in charge of air traffic control at the time). The CAA had no authority over military flights, which could enter controlled airspace with no warning to other traffic. The result was a series of near-misses and collisions involving civil and military aircraft, the latter often flying at much higher speeds than the former. For example, in 1958, the collision of United Airlines Flight 736 flying "on-airways" and an F-100 Super Sabre fighter jet near Las Vegas, Nevada, resulted in 49 fatalities.

Again, action was demanded. After more hearings, the Federal Aviation Act of 1958 was passed, dissolving the CAA and creating the Federal Aviation Agency (FAA, later renamed the Federal Aviation Administration in 1966). The FAA was given total authority over American airspace, including military activity, and as procedures and ATC facilities were modernized, mid-air collisions gradually became less frequent.

1956 Grand Canyon mid-air collision
U.S. National Register of Historic Places
U.S. National Historic Landmark
Location	Coconino County, Arizona
Coordinates	36°10′30″N 111°50′00″W
NRHP reference No.	14000280
Added to NRHP	April 22, 2014

On April 22, 2014, the site of the crash was declared a National Historic Landmark,[20] making it the first landmark for an event that happened in the air.[21] The location, in a remote portion of the canyon only accessible to hikers, has been closed to the public since the 1950s.[22][23]