1956 Grand Canyon Mid-air Collision - Flight History

Flight History

United Airlines Flight 718, a Douglas DC-7 Mainliner named Mainliner Vancouver, and flown by Captain Robert Shirley, First Officer Robert Harms, and Flight Engineer Gerard Fiore, departed Los Angeles International Airport at 9:04 AM PST with 53 passengers and five crew members aboard (including two flight attendants), bound for Chicago's Midway Airport. Climbing to an authorized altitude of 21,000 feet, Captain Shirley flew under instrument flight rules (IFR) in controlled airspace to a point northeast of Palm Springs, California where he turned left toward a radiobeacon near Needles, California, after which his flight plan was direct to Durango in southwestern Colorado. The DC-7, although still operating under IFR, was now "off airways"—that is, flying in uncontrolled airspace.

TWA Flight 2, a Lockheed L-1049 Super Constellation named Star of the Seine, with pilot Jack Gandy and copilot James Ritner in the cockpit, departed Los Angeles at 9:01 AM with 64 passengers (including 11 TWA off-duty employees who had won free tickets) and six crew members (including two flight attendants and an off-duty flight engineer), and headed to Kansas City Downtown Airport, 31 minutes behind schedule. Flight 2, initially flying IFR, ascended to an authorized altitude of 19,000 feet and stayed in controlled airspace as far as Daggett, California. At Daggett, Captain Gandy turned right to a heading of 059 degrees magnetic, toward the radio range near Trinidad, Colorado. The Constellation, like the DC-7, was now "off airways."

Shortly after takeoff, TWA's Captain Gandy requested permission to ascend to 21,000 feet to avoid thunderheads that were forming in the vicinity of his flight path. As was the practice at the time, his request had to be relayed by a TWA dispatcher to air traffic control (ATC), as neither flight 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 means of providing the horizontal separation required between two aircraft at the same altitude. Captain Gandy, requested "1,000 on top" clearance, which is still IFR, not VFR, and then was approved by ATC. "1,000 on top" clearance means he could climb to an altitude sufficient to place his aircraft 1,000 feet above the cloud tops along his flight path, but need to follows VFR, like own responsibility for separation, VFR altitude, etc. Flying VFR, however, placed the responsibility for maintaining safe separation from other aircraft upon Gandy and Ritner, a procedure referred to as "see and be seen." Upon receiving the "1,000 on top" clearance, Captain Gandy increased his altitude to 21,000 feet.

Both crews had estimated that they would arrive somewhere along the Painted Desert line at about 10:31 AM Pacific time. The Painted Desert line was about 200 miles long, running between the VORs at Bryce Canyon, Utah and Winslow, Arizona at an angle of 335 degrees relative to true north—wholly outside of controlled air space. Owing to the different headings taken by the two planes, TWA's intersection 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, now flying at the same altitude and nearly the same speed, the pilots were most likely maneuvering around towering cumulus clouds, though flying VFR required the TWA flight remain in clear air at all times. As they were maneuvering near the canyon, it is believed the planes simultaneously passed the same cloud formation on opposite sides, setting the stage for the collision.