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Delta Air Lines Flight 723 was a regularly scheduled passenger flight from Burlington, Vermont to Logan International Airport in Boston, Massachusetts, in the United States. An intermediate stop was made in Manchester, New Hampshire (MHT) enroute to Boston to pick up passengers stranded from cancellation of an earlier flight.

The aircraft used for the flight was a DC-9-31, which had been built in September 1967 and flew with the registration N975NE. The jetliner was one of the aircraft that Delta acquired in their 1972 merger with Northeast Airlines, to whom the aircraft was originally delivered.

On July 31, 1973 at 11:08AM, Delta Air Lines flight 723 crashed while landing at Logan International Airport. All 83 passengers on board as well as all six crew members died as a consequence of the accident. One of the passengers initially survived but died several months later on December 11, 1973. [1]

The aircraft had been vectored by Boston's air traffic control to a four mile course before final approach. The four mile distance was too short for a jet like the DC-9 to begin the final approach. Pilot error was also a factor. Following the air tower's commands, the pilots failed to recognize the danger of starting final descent at such a short distance from the runway. Because of this, the pilots were not able to stabilize the aircraft before landing.

Another major contributing factor to the crash was the instrumentation in the flight deck. An instrument called a flight director, which gives pitch (nose up or down) and roll (left turn or right turn) guidance had repeated discrepancies written-up in the aircraft log book. It was found that the flight director was in the go-around mode which commanded a nose-up pitch from the crew. The crew was likely distracted by the malfunctioning of the flight director and lost control of the aircraft trying to determine the reliability of the instrumentation. A recent upgrade of the cockpit avionics from the Sperry system to the Collins system was made at the time Northeast transisioned from Northeast to Delta following the merger in 1972 to standardize with Delta's DC-9 fleet.

The weather conditions at the time of the crash had cloud ceilings below 500 feet and 1/2 mile visibility in light winds. The flight director instrumentation was much needed in these types of conditions to successfully set up an approach to land on runway 4R at Boston. During the attempt of the ILS 4R approach, the DC-9 crashed into a seawall.

Many positive changes were made in aircraft maintenance after the accident in the years to come as a result of this accident in both aircraft maintenance and component design.

• NTSB Accident Report