Accident Overview

On June 30, 1956, a TWA Lockheed Super Constellation collided with a United Air Lines Douglas DC-7 over the Grand Canyon. Both aircraft fell into the canyon. There were no survivors among the 128 persons aboard the flights. The collision occurred while both of the regularly scheduled passenger service flights were flying under Visual Flight Rules (VFR).

Photo of United DC-7    Photo of Lockheed Super Constellation
Photo of United DC-7 (left) and Lockheed Super Constellation (right)
TWA Flight 2 and UAL Flight 718 Flight Plans
TWA Flight 2 and UAL Flight 718 Flight Plans
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Photo of United DC-7 and TWA Lockheed L-1049 (Constellation) parked next to each other at LAX
Photo of United DC-7 and a TWA Lockheed L-1049 (Constellation) parked next to each other at LAX
Photo copyright Michael McComb - used with permission

Photo of TWA cabin - wreckage
Photo of TWA cabin - wreckage

Flight Plans

TWA Flight 2, a regularly scheduled passenger service, was on an instrument flight rules (IFR) flight plan from Los Angeles, California to Kansas City, Missouri. The Lockheed Super Constellation was scheduled to depart Los Angeles at 8:30 a.m. and to fly an established controlled airway from Los Angeles through Daggett, California, and then fly to a series of direct points off controlled airways to Kansas City, Missouri. The TWA flight had a crew of six with 64 passengers. The flight plan proposed a cruising altitude of 19,000 feet and airspeed of 270 knots.

United Airlines Flight 718, a regularly scheduled passenger service, was on an instrument flight rules (IFR) flight plan from Los Angeles, California to Chicago, Illinois. The Douglas DC-7 was scheduled to depart Los Angeles at 8:45 a.m. and to fly an established controlled airway from Los Angeles through Palm Springs, California, and then to fly a series of direct points off controlled airways with a final destination of Chicago, Illinois. The United flight had a crew of five and 53 passengers. The flight plan proposed a cruising altitude of 21,000 feet and airspeed of 288 knots.

The TWA route would bring that flight initially on a more northerly route than the United flight, but the TWA and United flight paths would cross as TWA headed to Kansas City and UAL headed to Chicago. The planned flight paths would intersect before the Painted Desert line of position, over the Grand Canyon.

Chronology of Collision

After a 9:01 take-off from Los Angeles International Airport, TWA 2 was cleared by Los Angeles Air Route Traffic Control Center (ARTCC), or Los Angeles Center, for its en route clearance. The flight was approved for the climb to 19,000 feet in visual flight rules (VFR) conditions for the route to Daggett following an established controlled airway. United Air Lines Flight 718 took off from Los Angeles International Airport at 9:04 a.m., three minutes after TWA 2. United 718 was also given en route clearance by Los Angeles Center. The clearance corresponded to the flight plan as filed; however, the controller specified that the climb to assigned altitude be in VFR conditions. The pilots of both flights chose to fly off-airways after the initial portion of their flights (TWA to Daggett and UAL to Palm Springs) because the controlled airways beyond California were not as direct. Under the regulations at the time, flights were permitted off airways over direct courses provided that a flight plan was filed defining the direct route with several reporting points. There were numerous established company routes.


Photo of airplane props - wreckagePhoto of airplane props - wreckage

United 718 made a position report to Aeronautical Radio Inc., which held a contract with United, as it passed over Riverside and later over Palm Springs. When it reported passing over Palm Springs, United 718 indicated that it was still climbing to 21,000, and estimated it would reach Needles at 1000 and the Painted Desert line at 1034. Painted Desert was not a specific point, but a line of position. The Painted Desert line of Position extended northwest from the Winslow omni navigation station. The airplane's radio receiver could detect at what angle the plane was as it passed VOR (Very High Frequency Omni-directional range) radio transmitters. The airplane would be at the Painted Desert line of position when it was at 321 degrees from the Winslow omni radio station. The Civil Aeronautics Board (CAB) accident report has a flight track map that shows the controlled airways that both flights followed out of Los Angeles, and their subsequent direct flight paths and wreckage area.

Photo of airplane exit door - wreckage
Photo of airplane exit door - wreckage

At 9:21, through TWA company radio communications, TWA 2 reported that it was approaching Daggett, and requested a change in flight plan altitude assignment from 19,000 to 21,000 feet and, if unable, 1,000 on top to avoid turbulence. The request for "1000 on top" indicated that the flight would be at 1000 feet above the cloud layer/undercast, and allow the airplane to remain in VFR conditions relative to seeing other traffic. The request was forwarded by company radio to air traffic controllers at Los Angeles Center who contacted Salt Lake City control center, which monitored the airspace TWA was about to enter. Los Angeles said "TWA 2 is requesting two one thousand, how does it look? I see he is Daggett direct Trinidad, I see you have United 718 crossing his altitude - in his way at two one thousand." The Salt Lake City controller replied, "Yes, their courses cross and they are right together." The Los Angeles controller then called the TWA radio operator and said "Advisory, TWA 2, unable approve two one thousand." The TWA radio operator replied, "Just a minute. I think he wants a thousand on top, yes a thousand on top until he can get it." After determining from the flight, through the TWA radio operator, that it was then at least 1,000 on top, the Los Angeles Controller issued an amended clearance, "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 gave this clearance to TWA 2, further specifying that the United 718 flight was at 21,000 feet, and it was repeated back to him by the flight.

At approximately 0958 United 718 made a position report to the CAA communications station located at Needles stating that the flight was over Needles at 21,000 feet and estimated reaching the Painted Desert line of position at 1031. At 0959 TWA 2 reported its position to the company radio station in Las Vegas. It had passed Lake Mohave (at the Arizona border) at 0955 was 1,000 feet on top at 21,000 feet and would be reaching the Painted Desert line of position at 1031. This was the last communication with the flight.

Photo of buckles from airplane seat belts
Photo of buckles from airplane seat belts

Both flights were on uncontrolled direct routes as they left California. The CAA would later explain to the Civil Aeronautics Board that traffic information was not provided outside of controlled airspace, since such information would be of little value as many aircraft unknown to air traffic would be operating in the area. The CAA rules also specified that while an IFR flight is operating in VFR weather conditions, it is the responsibility of the pilot to avoid other aircraft, since VFR flights may be operating in the same area without the knowledge of air traffic control.

At 1031 an unidentified radio transmission was heard by Aeronautical Radio communicators at Salt Lake City and San Francisco. They were not able to understand the message when it was received, but it was later determined by playing back the recorded transmission that the message was from United 718. Context was interpreted as: "Salt Lake, United 718...ah...we're going in."

Click here to view Grand Canyon Mid-air Collision Animation including flight paths.

When neither flight reported passing the Painted Desert line of position and attempts to communicate with the flights were unsuccessful, a missing aircraft alert was issued. That evening, a pilot who operated flights over the Grand Canyon heard about the missing aircraft and had recalled seeing smoke rising out of the canyon earlier in the day. He returned to the area and was able to identify the empennage of the TWA Constellation. He reported that finding, and the next day made another flight, locating the second wreckage approximately one mile from the first. There were no signs of survivors.

Recovery and Investigation

In the days following the accident, the difficult process of investigation and recovery proceeded. The remoteness and topography of the crash sites made the process difficult. A team of Swiss mountaineers was brought in to assist in the recovery operation. After an exhaustive search for eyewitnesses and questioning of potential witnesses, the CAB concluded that there were no reliable eyewitness accounts of the collision.

Pieces of the TWA Super Constellation strewn over the Grand Canyon (left), DC-7 wreckage is removed by Helicopter (right)
Pieces of the TWA Super Constellation strewn over the Grand Canyon (left) from "The FAA a Historical Perspective" - used with permission
DC-7 wreckage is removed by Helicopter (right), Photo copyright Michael McComb - used with permission

The Civil Aeronautics Board (CAB) embarked upon the challenging task of reconstructing the collision based on the wreckage. Pieces of the left outer wing panel of the DC-7 were found. The lower skin was found to have evidence of the in-flight collision. Some of the collision evidence included red paint from the TWA airplane and fragments of the L-1049 de-icer boot. At the L-1049 wreckage area, a section of the DC-7 lower wing skin was found. This lower wing skin had evidence of contact with the cabin of the L-1049. The L-1049 empennage was found generally intact but at a large distance from the rest of the wreckage, indicating it had separated in-flight after the collision.

Photo of park rangers standing next to L-1049 tail
Photo of park rangers standing next to L-1049 tail
Photo copyright Michael McComb - used with permission

A large piece of fuselage skin from the upper right side of the L-1049 was also found to have evidence of the collision. These pieces of skin had paint marks from the DC-7 and metal smears indicating an object moving up and along the circumferential frames of the L-1049. Finally, there were propeller cuts found in pieces of lower and bottom fuselage of the L-1049. The paint marks at these cuts coincided with the paint scheme on the DC-7 propeller. Due to the difficulty in removing the wreckage from the canyon, much of the accident debris remains in the canyon today.

The CAB concluded that the initial impact occurred with the DC-7 slightly above and moving from right to left relative to the L-1049 and with the L-1049 moving to the right and aft relative to the DC-7. It appears that the first contact was the center fin leading edge of the L-1049, and the left aileron tip of the DC-7. Thereafter, the lower surface of the DC-7 left wing struck the upper aft fuselage of the L-1049 with disintegrating force. This force caused complete destruction of the L-1049 aft fuselage and destroyed the structural integrity of the DC-7 left wing outer panel. The aircraft continued to pass laterally, and the left fin leading edge of the L-1049 and the left wing tip of the DC-7 made contact, tearing off pieces of both. During this time, the DC-7 left propeller cut into the aft baggage compartment of the L-1049. This entire collision sequence occurred in less that one-half second.

Artist depiction of the collision appeared in TIME magazine's April 29, 1957 issue
Artist depiction of the collision appeared in TIME magazine
Photo copyright Michael McComb - used with permission

Seen on the right, this artist's depiction of the collision appeared in TIME magazine's April 29,1957 issue. It is a painting done by Milford Hunter, a scientific and technical illustrator with LIFE, and is based on the description of the collision as reconstructed in the CAB accident report.

The CAB also analyzed weather conditions at the time of the collision. In the area of the Grand Canyon where the collision occurred, there were several scattered cloud build-ups. The accident report states, "The build-ups were apparently formed in the lower clouds and protruded through and above them to approximately 25,000 feet." The report further states, "From the evidence available the Board is of the opinion that the weather conditions at 21,000 feet would not have precluded flight in VFR conditions in this accident area but that deviations may have been required to circumvent the buildups while the subject flights traversed the area." Based on United and TWA company procedures and the clearances that were given, the CAB concluded that both flights were operating according to rules prescribed for VFR conditions when the collision occurred. Here is a link to the "Analysis of Horizontal and Vertical Cloud Coverage", which is an attachment to the CAB accident report.

Based on both aircraft's estimates of time to reach the Painted Desert line of position, the aircraft should have been about 17 miles, or 3 ½ minutes flying time father east when the accident occurred. The board was not able to determine the reason for this delay, but did highlight several possibilities. These possibilities include that the airplanes were maneuvering to provide a more scenic view to the passengers, the wind was less favorable than expected, and the cloud buildups in the area may have required course deviations to get around the clouds.

The investigation of the collision and resulting CAB report also evaluated the ability of the pilots of the two aircraft to see and avoid each other. The CAB report discusses factors that inhibit the ability for pilots to see other aircraft in flight. Factors discussed include angular limits of cockpit vision, the distance that an object can be seen, the pilot's physical condition, and training. The CAB report points out that "aircraft converging on constant, unvarying collision courses may provide no relative motion when viewed from the aircraft". The CAB recognized the limitations of the "see and be seen" philosophy, and stated in their report, "This concept has existed as a matter of necessity, with its known limitations, and will continue until there are sufficient technological advances to provide additional assistance to the pilot for collision avoidance." The complete Accident Investigation Report, issued by the Civil Aeronautics Board, is available at the following link: Accident Investigation Report.

Memorials to the Victims

Two memorial sites were created for the passengers and crew members on the two airplanes. TWA arranged for a burial site at Citizen's Cemetery in Flagstaff, Arizona, where many of the victims from Flight 2 were interred. Many of the victims on United Flight 718 were buried in a site within the Grand Canyon National Park. The memorials are shown in the accompanying photographs.

Memorial at Grand Canyon Cemetery for victims of United Airlines Flight 718
Memorial at Grand Canyon Cemetery for victims of
United Airlines Flight 718


Photo of TWA gravesite at Citizen’s Cemetery in Flagstaff, Arizona
Photo of TWA gravesite at Citizen’s Cemetery in Flagstaff, Arizona
Photo of a plaque list 66 victims of TWA Flight 2 interred at Citizen's Cemetery
Photo of a plaque list 66 victims of TWA Flight 2 interred at Citizen's Cemetery

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