TheGrand Canyon mid-air collision occurred in thewesternUnited States on June 30, 1956, when aUnited Air LinesDouglas DC-7 struck aTrans World AirlinesLockheed L-1049 Super Constellation overGrand Canyon National Park,Arizona. The first plane fell into thecanyon while the other slammed into a rock face. All 128 on board both airplanes died, making it the first commercial airline incident to exceed one hundred fatalities. The airplanes had departedLos Angeles International Airport minutes apart from each other and headed forChicago andKansas City, respectively.The collision took place in uncontrolled airspace, where it was the pilots' responsibility to maintainseparation ("see and be seen"). This highlighted the antiquated state of air traffic control, which became the focus of major aviation reforms.

1956 Grand Canyon mid-air collision
United Air Lines Flight 718 · TWA Flight 2

Accident
Date	June 30, 1956 (1956-06-30)
Summary	Mid-air collision due to inadequateATC system
Site	Grand Canyon,Arizona, United States
Total fatalities	128
Total survivors	0
First aircraft
A United Air Lines DC-7, similar to the aircraft involved
Type	Douglas DC-7 Mainliner
Name	Mainliner Vancouver
Operator	United Air Lines
IATA flight No.	UA718
ICAO flight No.	UAL718
Call sign	UNITED 718
Registration	N6324C[1]
Flight origin	Los Angeles International Airport,California, United States
Destination	Chicago Midway Airport,Illinois, United States
Occupants	58
Passengers	53
Crew	5
Fatalities	58
Survivors	0
Second aircraft
N6902C, the Lockheed L-1049A Super Constellation involved
Type	Lockheed L-1049A Super Constellation
Name	Star of the Seine
Operator	Trans World Airlines
IATA flight No.	TW2
ICAO flight No.	TWA2
Call sign	TWA 2
Registration	N6902C[2]
Flight origin	Los Angeles International Airport,California, United States
Destination	Kansas City Downtown Airport,Kansas City,Missouri, United States
Occupants	70
Passengers	64
Crew	6
Fatalities	70
Survivors	0

450km
280miles

   

Location of the collision

Trans World Airlines Flight 2, aLockheed L-1049 Super Constellation namedStar of the Seine, withCaptain Jack Gandy (age 41),First Officer James Ritner (31), andFlight Engineer Forrest Breyfogle (37), departed Los Angeles on Saturday, June 30, 1956, at 9:01 am PDT with 64 passengers (including 11 TWA off-duty employees on free tickets) and six crew members (including twoflight attendants and an off-duty flight engineer), and headed toKansas City Downtown Airport, 31 minutes behind schedule. Flight 2, initially flying underinstrument flight rules (IFR), climbed to an authorizedaltitude of 19,000 feet (5,800 m) and stayed in controlled airspace as far asDaggett, California. At Daggett, Captain Gandy turned right to a heading of 059 degrees magnetic, toward theradio range nearTrinidad, Colorado.^[3] The Constellation was now "off airways", otherwise known as flying inuncontrolled airspace.^[4]

United Air Lines Flight 718, aDouglas DC-7 namedMainliner Vancouver, was piloted by Captain Robert "Bob" Shirley (age 48), First Officer Robert Harms (36), and Flight Engineer Girardo "Gerard" Fiore (39). They departed Los Angeles at 9:04 am PDT with 53 passengers and 5 crew members aboard (including two flight attendants), bound for Chicago'sMidway Airport. Climbing to an authorized altitude of 21,000 feet (6,400 m), Captain Shirley flew under IFR incontrolled airspace to a point^{[note 1]} northeast ofPalm Springs, California, where he turned left toward a radio beacon nearNeedles, California, after which his flight plan was direct to Durango in southwestern Colorado.^{[note 2]} United's DC-7, though still under IFR, was now, like TWA's Constellation, en route in uncontrolled airspace.

Shortly after takeoff TWA's Captain Gandy requested permission to climb to 21,000 feet to avoidthunderheads that were forming near his flight path. As was the practice at the time, his request had to be relayed by a TWAflight dispatcher to air traffic control (ATC), as neither crew was in direct contact with ATC after departure. ATC denied the request; the two airliners would soon be reentering controlled airspace (the Red 15 airway running southeast from Las Vegas) and ATC had no way to provide the horizontal separation required between two aircraft at the same altitude.

Captain Gandy then requested "1,000 on top" clearance (flying 1,000 feet (300 m) above the clouds, and thus invisual meteorological conditions). This was approved by ATC, and meant that the Constellation was still under IFR but free of separation restrictions normally applied by ATC. It transferred to Gandy and Ritner the responsibility for maintaining safe separation from other aircraft, on the principle then termed "see and be seen" (more recently "see and avoid").

This division of responsibilities between aircrew and ATC is especially useful when two aircraft are transitioning to or from an airfield approach when VFR conditions exist above cloud layers.^[5] It is less common en route.

Upon receiving "1,000 on top" clearance, Captain Gandy increased his altitude to 21,000 feet (6,400 m).^[3] Both crews were then at this altitude, and both had estimated that they would cross thePainted Desert line at about 10:31 am Pacific time.^[6][7] The Painted Desert line was about two hundred miles (320 km) long, running between theVORs atBryce Canyon, Utah, andWinslow, Arizona, at an angle of 335 degrees relative totrue north – wholly outside of controlled air space. Owing to the different headings taken by the two planes, TWA's crossing of the Painted Desert line, assuming no further course changes, would be at a 13-degree angle relative to that of the United flight, with the Constellation to the left of the DC-7.

As the two aircraft approached the Grand Canyon, at the same altitude and nearly the same speed, the pilots were likely maneuvering around towering cumulus clouds. (The Constellation's clearance required it to stay in clear air – andabove cloud.) As they were maneuvering near the canyon, it is believed the planes passed the same cloud on opposite sides.^[8]

At about 10:30 am, the two aircraft collided over the canyon at an angle of about 25 degrees.^[9]  Post-crash analysis determined that the United DC-7 was banking to the right and pitching down at the time of the collision, suggesting that one or possibly both of the United pilots spotted the TWA Constellation and attempted evasive action.^[10]

The DC-7's upraised left wing clipped the top of the Constellation'svertical stabilizer and struck thefuselage immediately ahead of the stabilizer's base, causing thetail assembly to break away from the rest of theairframe.^{[citation needed]} Thepropeller on the DC-7's left outboard, or number oneengine, concurrently chopped a series of gashes into the bottom of the Constellation's fuselage.Explosive decompression would have instantaneously occurred from the damage, a theory substantiated by light debris, such as cabin furnishings and personal effects, being scattered over a large area.

The separation of the tail assembly from the Constellation resulted in immediate loss of control, causing the aircraft to enter a near-vertical,terminal velocity dive.^{[citation needed]} Plunging into the Grand Canyon at an estimated speed of more than 700 feet per second (410 kn; 480 mph; 770 km/h), the Constellation slammed into the north slope of a ravine on the northeast slope ofTemple Butte and disintegrated on impact, instantly killing all aboard. An intense fire, fueled byaviation gasoline, ensued. The severed tail assembly, badly battered but still somewhat recognizable, came to rest nearby.

The DC-7's left wing to the left of the number one engine was mangled by the impact and was no longer capable of producing substantiallift. The engine had been severely damaged as well, and the combined loss of lift and propulsion left the crippled airliner in a rapidly descending left spiral from which recovery was impossible.^[4] TheMainliner collided with the south sidecliff ofChuar Butte and disintegrated, instantly killing all aboard.

The airspace over the canyon was not under any type ofradar observation and there were nohoming beacons,cockpit voice recorders, orflight 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 inSalt Lake City andSan Francisco heard a garbled transmission from Flight 718 (the DC7), the last from either aircraft.^{[citation needed]}Civil Aeronautics Board (CAB)accident investigation engineers later deciphered the transmission – which had been preserved onmagnetic 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 theColorado andLittle Colorado Rivers by Henry and Palen Hudgin, two brothers who operatedGrand Canyon Airlines, a small air taxi service.^[12] During a trip earlier in the day, Palen had noted dense black smoke rising nearTemple Butte, the crash site of the Constellation, but had dismissed it as brush set ablaze bylightning.

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 (aPiper Tri-Pacer) deep into the canyon and searched near the location of the smoke. The Constellation'sempennage was found, and the brothers reported their findings to authorities. The following day, the two men pinpointed the wreckage of the DC-7. Numeroushelicopter 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 unpredictableair currents.^[13]

The airlines hired theSwiss 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.^{[citation needed]}

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,^[15] at the canyon's south rim.^{[citation needed]} Twenty-nine unidentified victims of the United flight were interred in four coffins at theGrand Canyon Pioneer Cemetery. Sixty-six of the seventy TWA passengers and crew are buried in a mass grave at Citizens Cemetery inFlagstaff, Arizona. A number of years elapsed following this accident before most of the wreckage was removed from the canyon. Some pieces of the aircraft still remain at the crash sites.

The investigation of this accident, led byJack Parshall, was particularly challenging due to the remoteness andtopography 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 andairworthiness of the two planes were thought to have played no role in the accident. Lackingcredible 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 contributoryhuman 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 withLife 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 detailedgouache painting first appeared inLife's April 29, 1957, issue^[17] and was subsequently included in David Gero's 1996 edition ofAviation Disasters II.

In a letter to Gero in 1995, Hunter wrote:^{[note 3][citation needed]}

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 forLife. 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 disagreed 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, surpassingUnited Air Lines Flight 409 the year before.^[19] It was surpassed in both respects on December 16, 1960, by the1960 New York mid-air collision. Coincidentally, the collision also involved United and TWA and saw 128 deaths in the two aircraft (in addition to 6 deaths on ground). However, it is still the deadliest aviation disaster in the state of Arizona.

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. Theair 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."^[20]

The accident was particularly alarming in that public confidence inair travel had increased during the 1950s with the introduction of new airliners like theSuper Constellation,Douglas DC-7, andBoeing Stratocruiser. Travel by air had become routine for large corporations, andvacationers often considered flying instead of traveling bytrain. At the time, acongressional 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.

Asnear-misses and mid-air collisions continued, the public demanded action. Often-contentiouscongressional 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 themilitary and theCivil Aeronautics Administration (CAA, thefederal 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 andmilitary aircraft, the latter often flying at much higher speeds than the former. For example, in 1958, the collision ofUnited Air Lines Flight 736 flying "on-airways" and anF-100 Super Sabre fighter jet nearLas Vegas, Nevada, resulted in 49 fatalities.

Again, action was demanded. After more hearings, theFederal Aviation Act of 1958 was passed, dissolving the CAA and creating theFederal Aviation Agency (FAA, later renamed theFederal 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.

In 1960, a jury in Kansas City, in a judgment against United Air Lines, awarded the estate of Jack S. Gandy, the pilot of the TWA flight, $64,000 (equivalent to $680,000 in 2024), and the estate of James H. Ritner, the co-pilot, $45,000 (equivalent to $480,000 in 2024).^[21]

On April 22, 2014, the site of the crash was declared aNational Historic Landmark,^[22][23] making it the first landmark for an event that happened in the air.^[24] The location, in a remote portion of the canyon accessible only to hikers, has been closed to the public since the 1950s.^[25][26]

In 2006, the story of this disaster was covered in the third season of the History Channel programUFO Files. The episode, entitled "Black Box UFO Secrets", contained the Universal Newsreel footage of the accident narrated byEd Herlihy.^[27]

In 2010, the story of the disaster, along with other mid-air collisions, was featured on the eighth season of theNational Geographic Channel showMayday (also known asAir Emergency andAir Crash Investigation). The special episode is entitled "System Breakdown".^[28] In 2013, an episode from the twelfth season, entitled "Grand Canyon Disaster", also featured this accident.^[29]

It is featured in season 1, episode 5, of the TV showWhy Planes Crash, in an episode called "Collision Course".

In 2015, the first season ofMysteries at the National Parks on the Travel Channel, in the series' seventh episode, "Portal To The Underworld," the crash was also featured and was mentioned as being a "supernatural event."In 2014, the Smithsonian channel show "Air Disasters" episode 4 season 6 covered the event and investigation in episode "Grand Canyon".

• Aeroméxico Flight 498
• 1996 Charkhi Dadri mid-air collision
• Free flight (air traffic control)
• Gol Transportes Aéreos Flight 1907
• 1986 Grand Canyon mid-air collision, another airliner involved in a mid-air collision over the Grand Canyon
• Hughes Airwest Flight 706
• 2001 Japan Airlines mid-air incident
• List of National Historic Landmarks in Arizona
• National Register of Historic Places listings in Coconino County, Arizona
• 1960 New York mid-air collision, which also involved aircraft fromUnited Air Lines andTrans World Airlines
• Pacific Southwest Airlines Flight 182
• 1922 Picardie mid-air collision
• 2002 Überlingen mid-air collision
• 1976 Zagreb mid-air collision

• Civil Aeronautics Board Official Report, Docket 320, File 1, issued on April 17, 1957
• Air Disaster, Vol. 4: The Propeller Era, byMacarthur Job, Aerospace Publications Pty. Ltd. (Australia), 2001.ISBN 1-875671-48-X
• Blind Trust, byJohn J. Nance, William Morrow & Co., Inc. (US), 1986,ISBN 0-688-05360-2

• "Civil Aeronautics Board Accident Investigation Report"(PDF).Federal Aviation Administration. Archived fromthe original(PDF) on February 20, 2015. –Alternate URL withPDF
• "TWA Flight 2 and UAL Flight 718 Flight Plans". Federal Aviation Administration. Archived fromthe original on March 22, 2014. RetrievedMarch 20, 2014.
• Cadwalader, Mary H. (April 29, 1957)."Air Mystery is Solved".Life. pp. 151–164.
• Lessons from Tragedy Over the Grand Canyon by Jon Proctor
• Flying Blind by Gregory Rawlins
• TWA and United collision over Grand Canyon Arizona Aircraft Archaeology
• What Caused The "Worst Accident In The History" Of Commercial Aviation? Mayday: Air Disaster – YouTube Channel