CIVIL AERONAUTICS BOARD
AIRCRAFT ACCIDENT REPORT
NORTHWEST AIRLINES, INC.
BOEING 720B, N724US
NEAR MIAMI, FLORIDA
FEBRUARY 12, 1963
Northwest Airlines, Inc., Boeing 720B, N724US, operating as Flight 705, crashed in an unpopulated area of the Everglades National Park, 37 miles west—southwest of Miami International Airport at approximately 1350 e. s. t., on February 12, 1963. All 35 passengers and the crew of eight were fatally injured.
Flight 705 departed Miami at 1335 e.s.t. Circuitous routing was utilized during the climbout in an effort to avoid areas of anticipated turbulence associated with thunderstorm activity. At 1347 e.s.t., in response to a request for their position and altitude, the flight advised, "We're just out of seventeen five (17,500 feet) and stand by on the DME one." This was the last known transmission from the flight. Shortly thereafter the aircraft entered a steep dive, during which the design limits were exceeded and the aircraft disintegrated in flight.
The Board determines that the probable cause of this accident was the unfavorable interaction of severe vertical drafts and large longitudinal control displacements resulting in a longitudinal upset from which a successful recovery was not made.
Northwest Airlines, Inc, Boeing 720B, N724US, operating as Flight 705, crashed in an unpopulated area of the Everglades National Park, 37 miles west-southwest of Miami International Airport at approxiately 1350 on February 12, 1963. All 35 passengers and the crew of eight were fatally injured.
The aircraft arrived in Miami at 1240, following a routine flight from Chicago, Illinois. The captain of the inbound flight reported that the only mechanical discrepancy was "... the cuflow valves being a little sticky merely made it a little difficult to maintain the pressurization in a smooth manner..." These valves were cleaned, and a leaking rivet at the No. 4 reserve fuel tank was plugged when it was noticed by the mechanic. This was the only maintenance performed during the "turnaround."
- All times herein are eastern standard for February 12, 1963, based on the 24-hour clock.