Question: What caused the plane crash that killed Annette Snell?

Context articles: Southern by the Grace of God
Turkish Airlines Flight 981
The plane crash (Neighbours)
Clifton Williams
PMTair Flight 241
Southern Airways Flight 242
Andy Tyson
Annette Snell
James Heathman
Lynyrd Skynyrd Tribute Tour

Southern by the Grace of God is a live album by southern rock band Lynyrd Skynyrd, this live concert was a tribute by Lynyrd Skynyrd to the members of the band who had died in the 1977 plane crash.
 The plane crash killed frontman Ronnie Van Zant, guitarist Steve Gaines, backing vocalist Cassie Gaines and road manager Dean Kilpatrick.
 This is the first album produced by the band after the '77 plane crash.
 The band's lineup was re-worked into a second-generation Skynyrd.
 The changes include: Johnny Van Zant, younger brother of Ronnie Van Zant, taking over on vocals, Ed King, who departed the band during a 1975 tour and Randall Hall, who replaced the paralyzed Allen Collins.
 The three (King, Hall along with founding member Gary Rossington) re-form the famous triple-lead guitar attack of the original band.
 New background vocalists Carol Bristow and Dale Krantz-Rossington were added to take the place of the original Honkettes.
Turkish Airlines Flight 981 was a regularly scheduled flight from Istanbul Yesilköy Airport to London Heathrow Airport with an intermediate stop in Paris at Orly Airport.
 On 3 March 1974, the McDonnell Douglas DC-10 operating the flight crashed into the Ermenonville Forest, outside Paris, killing all 346 people on board.
 At the time, it was the deadliest plane crash in aviation history.
 It still remains the fourth-deadliest plane crash in aviation history, is the deadliest involving a DC-10, the second deadliest with no survivors, the deadliest single-plane crash with no survivors, the deadliest to have occurred on French soil, and the second worst aviation accident in Europe.
 The crash was also known as the Ermenonville air disaster, from the forest where the aircraft crashed.
"The plane crash" is a storyline from the Australian television soap opera "Neighbours" that began on 24 October 2005 when an aeroplane, carrying several characters, crashed in Bass Strait after a bomb was detonated during the journey.
 The storyline aired as part of the show's 20th anniversary and would be the catalyst for several major storylines that aired the following year.
 "The plane crash" also saw the departures of three established characters; David (Kevin Harrington), Liljana (Marcella Russo) and Serena Bishop (Lara Sacher).
 The actors' departures had been announced in May 2005, but it was not confirmed they would depart during "The plane crash" until their last scenes aired.
Clifton Curtis "C.C." Williams Jr. (September 26, 1932 – October 5, 1967), (Major, USMC), was an American naval aviator, test pilot, mechanical engineer, Major in the United States Marine Corps, and NASA astronaut, who was killed in a plane crash; he had never been to space.
 The crash was caused by a mechanical failure in a NASA T-38 jet trainer, which he was piloting to visit his parents in Mobile, Alabama.
 The failure caused the flight controls to stop responding, and although he activated the ejection seat, it did not save him.
 He was the fourth astronaut from NASA's Astronaut Group 3 to have died, the first two (Bassett and Freeman) having been killed in separate T-38 flights and (Chaffee) in the Apollo 1 fire earlier that year.
 The aircraft crashed in Florida near Tallahassee within an hour of departing Patrick AFB.
PMTair Flight 241 (U4 241/PMT241) was a scheduled domestic passenger flight, flying from Siem Reap International Airport, Siem Reap to Sihanoukville International Airport, Sihanoukville.
 The flight was operated by PMTair using an Antonov An-24.
 On 25 June 2007, the Antonov An-24, registered as XU-U4A, disappeared over Cambodian jungle near Bokor while on approach to Sihanoukville.
 A massive search and rescue operation occurred, as thousands of soldiers and police scoured the area.
 The aircraft was found to have crashed in southwestern Cambodia, northeast of Bokor Mountain in Kampot Province.
 All 22 people on board, most of whom were South Korean tourists, were killed.
 The crash was the second deadliest plane crash in Cambodia's history and the worst plane crash in Kampot Province.
 An investigation and inquiry was completed in March 2008, but couldn't conclude the cause of the crash of Flight 241.
Southern Airways Flight 242 was a DC-9-31 jet, registered N1335U, that executed a forced landing on a highway in New Hope, Paulding County, Georgia, United States after suffering hail damage and losing thrust on both engines in a severe thunderstorm on April 4, 1977.
Andy Tyson (October 15, 1968 – April 10, 2015) was an American businessman, writer, and mountaineer who died in April 2015 in a small plane crash, at the age of 46.
 At the time of his death he was working for the company Creative Energies.
 He died with several others in a plane crash at Diamond D ranch in the U.S. State of Idaho.
 The plane was a Cessna T210M and it crashed in Custer County, Idaho.
 (see Cessna 210) In the crash investigation it was noted that wind currents in Mountain areas can push small planes around.
 A candlelight vigil to mourn the lost gathered 600 people in the locality.
 The fund had the goal of raising 100 thousand USD to help those in underdeveloped areas near climbing areas, develop mountaineering skills.
Annette Snell (March 22, 1945 – April 4, 1977) was an American rhythm and blues singer who recorded in the 1960s and 1970s.
 She died in the Southern Airways Flight 242 crash.
James Easter Heathman (April 7, 1917 – January 29, 2008), also known as J. E. Heathman, was an American former farmer and U.S. Army veteran, who, as a teenager in 1931, witnessed and discovered the crash of a Transcontinental & Western Air airliner, which killed eight people, most notably University of Notre Dame football coach, Knute Rockne.
 Heathman, who was 13 years old at the time he discovered the plane crash with his father on March 31, 1931, was the last living witness to the plane crash.
 Heathman later became a Knute Rockne historian and often led free tours of Notre Dame fans to the site of the crash, especially during the last 20 years of his life.
The Lynyrd Skynyrd Tribute Tour was a tour that was undertaken to pay tribute to the original band members who died in a plane crash in 1977.
 The tour began in the fall of 1987, in honor of the 10-year anniversary of the plane crash.
 A number of surviving members reunited for the tour.
 Original members Gary Rossington, Billy Powell and Leon Wilkeson were joined by Ed King (original member who had left the band in 1975), Artimus Pyle (drummer at the time of the plane crash), Randall Hall and Johnny Van Zant.