[1] The co-pilot, Roger Marshall Whitezell, born on September 6, 1930, was newer to United than Captain Towle.

The control tower at O'Hare lost radio contact with the plane as it approached the western shore of Lake Michigan.

A tower crewman at O'Hare said the pilot had just received landing instructions and had replied "Roger" when communication with the plane failed.

Wallace Whigam, a lifeguard for the Chicago Park District, reported from the North Avenue Beach House that he had seen an orange flash on the horizon.

The Coast Guard reported that skin divers had assembled at the North Shore Yacht Club in Highland Park, which was used as an informal search base.

Hours after the crash, members of the Civil Aeronautics Board (the predecessor to the NTSB) were on scene to begin investigating the accident.

[7] The NTSB estimated the plane was traveling at a speed of approximately 200 knots (230 mph; 370 km/h) when it impacted the water.

The investigation was hampered by the fact that the flight data recorder (FDR) was not recovered from the wreckage, which was in muddy water 250 feet (76 m) deep.

"[1] The first proven case of a crash caused by a pilot misreading the altimeter by 10,000 feet (3,000 m) was of a BEA Vickers Viscount outside Ayr, Scotland, on April 28, 1958.

[8] The second proven case was the 1958 Bristol Britannia 312 crash near Christchurch, Dorset, in the south of England, on December 24, 1958.