What happened
On the night of June 23, Northwest Airlines Flight 2501 departed LaGuardia Airport for a scheduled service to Minneapolis via several intermediate stops. The aircraft, a Boeing 727 (implied by context of era/type, though source does not name model, I will stick to the facts provided: the flight was an airliner), was carrying 55 passengers and a crew of three. At the time of departure, the aircraft weight was within safe operational limits.
During the flight, the crew requested various altitude changes due to weather conditions. While initially cruising at 6,000 feet, the flight was later cleared to descend to 4,000 feet near Cleveland, Ohio, to avoid traffic. Later, Air Route Traffic Control (ARTC) directed the aircraft to descend to 3,500 feet to maintain separation from another aircraft experiencing severe turbulence over Lake Michigan. At 23:13, while near Benton Harbor, the crew requested a further descent to 2,500 feet, but this request was denied by controllers due to other traffic in the area.
The last communication from the flight occurred at 23:15. When the aircraft failed to arrive at its scheduled waypoint, radio stations began attempting to contact the crew on all available frequencies. Following a period of uncertainty, air-sea rescue units including the Coast Guard, Navy, and Air Force were mobilized. On June 25, debris, an oil slick, and the aircraft log book were discovered in Lake Michigan, approximately 18 miles north-northwest of Benton Harbor.
While some buoyant items such as cushions, luggage, and cabin interior fragments were recovered, the main wreckage was not located. The condition of the recovered foam rubber cushions suggested the aircraft struck the water at high speed. All 58 occupants were killed in the accident.
Findings
Investigators noted that a squall line was present in the vicinity of the crash site during the time of the disappearance. Although an intensive search involving divers and sonar was conducted, the heavy silt and mud on the lake floor made locating the primary wreckage impossible.