Independent Air Flight 1851

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Independent Air Flight 1851
Independent Air - Skylarks Boeing 707-331B N7231T (26022307271).jpg
N7231T, the aircraft involved seen 4 years before the accident
Date8 February 1989
SummaryControlled flight into terrain due to pilot error and ATC error
SitePico Alto,
Santa Maria Island, Azores
36°58′53″N 25°05′28″W / 36.981475°N 25.091008°W / 36.981475; -25.091008Coordinates: 36°58′53″N 25°05′28″W / 36.981475°N 25.091008°W / 36.981475; -25.091008
Aircraft typeBoeing 707-331B
OperatorIndependent Air
Flight originOrio al Serio Airport, Bergamo, Italy
StopoverSanta Maria Airport,
Santa Maria, Azores
DestinationPunta Cana,
Dominican Republic

On 8 February 1989, Independent Air Flight 1851, a Boeing 707 on an American charter flight from Bergamo, Italy to Punta Cana, Dominican Republic, struck Pico Alto while on approach to Santa Maria Airport in the Azores for a scheduled stopover. The aircraft was destroyed, with the loss of all 144 on board, resulting in the deadliest plane crash in Portugal's history. Due to the large number of tourists from Italy that perished in this tragedy, it is known in this country as Il disastro delle Azorre” (Italian for “The disaster of the Azores”).

Aircraft and crew[edit]


The aircraft was a 19-year-old Boeing 707 (Serial no. 19572, factory no. 687) that had been built in 1968, and made its first flight on 22 March the same year. It had been previously operated by Trans World Airlines (TWA).[2]


The flight crew consisted of Captain Leon James Daugherty, 41-year-old, first officer Sammy Adcock, 36, and flight engineer Jorge Gonzalez, 34.[3]

Daugherty had 7,766 flying hours, including 766 hours on the Boeing 707 (278 as first officer and 488 hours as captain, respectively). He also had 2,259 hours on the Boeing 727 (347 hours as first officer and 1,912 hours as captain, respectively).[4]

Adcock had a total of 3,764 flying hours, including 64 hours in the Boeing 707. Gonzalez had a total of 6,756 flying hours, including 1,056 hours on the Boeing 707, He also had 2,888 hours on the Boeing 727 and 2,823 hours on the Lockheed C-5 Galaxy.[4]


The official investigation determined that during approach to Santa Maria Airport, the air traffic controller instructed the crew to descend to 3,000 feet (910 m) for an ILS approach to runway 19.[4]

During that transmission, a trainee controller had also transmitted an incorrect QNH (barometric altimeter setting) that was 9 hPa too high. The approach instructions were not fully heard since the pilot had re-keyed his microphone to acknowledge the new QNH, and likely did not hear the second repeat of the 3,000 ft safe altitude, declaring: "We’re re-cleared to 2,000 feet..." (610 m). Although the first officer questioned the barometric altitude, the captain agreed that the first officer had heard the read-back correctly.

After having been cleared to the ILS approach, the crew failed to accomplish the approach briefing, missing an opportunity to notice the 3,000 ft minimum safe altitude and the presence of Pico Alto.

Leveling off at 2,000 feet (610 m), the airliner experienced heavy turbulence near Santo Espírito and subsequently impacted the ridge of Pico Alto in a level attitude at an altitude of 1,795 feet (547 m). There was no evidence of any in-flight emergency and the altimeter was found correctly set to 1027 mb.


The Board of Inquiry concluded that the accident was due to non-observance by the crew of established operating procedures which led to the deliberate descent of the aircraft to 2000 feet when the published minimum sector altitude was 3000 feet. It also found that the controller had put the aircraft 240 feet (73 m) below that indicated on board the aircraft, exacerbating the original error by the first officer.[4]

Other factors:

  • Bad communications techniques on the part of the co-pilot and controller, including the non-adherence to standard phraseology in some of the ground communication.
  • Neglecting aerodrome control tower procedures in not requesting a readback of the descent clearance.
  • The limited international flying experience of the crew and the airline's deficient crew training that did not include emergency maneuvering techniques for terrain avoidance.
  • Non-compliance with the National Institute of Civil Aviation of Portugal Aeronautical Information Publications (flight plan procedures and authorized routes).


In 1992, a group of next-of-kin claimed Independent Air and the lessor of the aircraft, International Air Leases, were responsible for the loss of their relatives and wanted to be compensated. In the court cases that followed, Independent Air was judged to be negligent based on the following statement: "undisputed facts show that the pilot and crew flew the plane below an altitude of 3,000 feet, when their charts of the area clearly showed that it was dangerous to go below 3,000 feet because of the mountain. The pilot in command cannot excuse his act by alleging the air traffic controller directed him to descend to an altitude of 2,000 feet and gave him an incorrect altimeter setting. In descending below the safe indicated altitude, he knowingly placed the plane in a dangerous situation. He then proceeded to fly into the top of the mountain that he knew was there".[5] The case was settled for $34,000,000.[6]


  1. ^ "FAA Registry (N7231T)". Federal Aviation Administration.
  2. ^ "JetPhotos.Net » Aircraft Census Database » CN 19572 Boeing 707-331B N7231T". Retrieved 2018-11-20.
  3. ^ New York Times (1989-02-09). "Charter Jet Crash in Azores Kills 144". New York Times. Associated Press.
  4. ^ a b c d Duke, Thomas A. (February 1995). "Aircraft Descended Below Minimum Sector Altitude and Crew Failed to Respond to GPWS as Chartered Boeing 707 Flew into Mountain in the Azores" (PDF). Accident Prevention. Vol. 52 no. 2. Flight Safety Foundation. Archived (PDF) from the original on 16 November 2012.
  5. ^ "Independent Air vs Tosini".
  6. ^ "Spenser & Krause – Our Work and Past cases".
  • UK CAA (April 1976), CAA Document 429: World Airline Accident Summary, ICAO

Further reading[edit]

External links[edit]