Any fatal plane crash is a tragedy; that's not in question. However, one horrific step beyond that is the suggestion that a pilot or other company employee would bring a plane down deliberately in an act of purported suicide, killing themselves and mass-murdering the passengers and crew who were in their professional care.
This list examines some plane crashes around the world that were attributed to pilot/airline employee suicide.
5 Germanwings Flight 4U9525, March 24, 2015 (150 Fatalities)
Andreas Lubitz was employed by Germanwings as a first officer on the popular Airbus A320 aircraft. He reportedly enjoyed being a pilot but had suffered various episodes of mental illness during his training which his employer was aware of. However, they were not aware that Lubitz had been declared "unfit to work" by his doctor before he arrived to fly his aircraft from Barcelona to Dusseldorf on March 24th, 2015.
The aircraft crashed into the French Alps approximately one minute after its last routine contact with Air Traffic Control and after the Captain had left the cockpit to use the restroom. While alone in the cockpit, Lubitz reportedly locked the Captain out and pushed the controls forward, putting the plane into a controlled descent that ended in the impact with the mountain about ten minutes later. All 144 passengers and six crew members were killed in the impact. This tragedy also helped bring in new legislation around the world that stated no pilot should be left on their own in the cockpit at any time, necessitating that a qualified crew member takes their place whenever a pilot needs to leave the flight deck.
4 Pacific Southwest Airways (PSA) Flight 1771, December 7, 1987 (43 Fatalities)
David Burke was an employee of PSA's parent company US Air, who had recently been dismissed for theft from the in-flight bar takings, totalling sixty-nine dollars. Burke had met that day with his former boss Ray Thompson for an appeal hearing to attempt to get his job reinstated, but Thompson had upheld his dismissal.
After leaving Thompson's office, Burke went straight to buy a ticket for flight 1771; knowing Ray Thompson caught the flight daily to commute to and from work. Because he was still carrying his airline credentials, Burke was able to bypass security screening and take a .44 calibre handgun onto the plane. Once airborne, Burke made his presence known to Thompson, through a note, he wrote on an airsickness bag. He then went to the restroom, loaded his gun and returned to the cabin, where he shot Thompson twice at point blank range. He then shot a flight attendant, both pilots and another PSA pilot who was a passenger on the plane. Finally, Burke entered the cockpit, pushed the throttles to full power and the control column at the ground. The plane was travelling faster than the speed of sound before it hit, impacting the ground at around 770 mph. The plane was obliterated, along with all remains of the 43 people on board.
3 Linhas Aéreas de Moçambique (LAM), Flight 470, November 29, 2013 (33 Fatalities)
A scheduled flight from Mozambique to Angola, flight 470 was uneventful until almost two hours into the flight, when it commenced a sudden descent from 38,000 feet and impacted with the ground a few minutes later.
It transpired that when the co-pilot had left the cockpit to go to the restroom, the Captain had locked him out, before altering the flight settings to descend rapidly through lower altitudes at high speed. The co-pilot could be heard pounding on the cockpit door to gain entry and try to save the flight. However, he was unsuccessful. After 9/11, cockpit doors were reinforced to prevent potential hijackers getting access, but this also had the unfortunate side-effect of preventing excluded crew members re-entering too. (This was also the case in the Germanwings crash almost 18 months later-see item 1.)
Various theories exist for why the Captain acted the way he did, although it was reported that he had lost his son the year before and was allegedly having marital problems at the time of the crash. 27 passengers and six crew members were killed.
2 SilkAir Flight 185, December 19, 1997 (104 fatalities)
A controversial investigation, SilkAir flight 185 was alleged to have been brought down deliberately by the Captain, supposedly due to his debt and other personal problems. Subsequent investigations, however, have questioned these original findings.
The Captain was reported to have left the cockpit, disconnecting the plane's voice recorder as he left, so that his subsequent actions would not be recorded for investigators to hear. When he returned, he would have had to either incapacitate his co-pilot or find some excuse to make him leave the flight deck so that he could also switch off the flight data recorder, before putting the plane into a rapid descent from which it couldn't be recovered.
Due to the lack of reliable 'black box' data, much of the investigators findings had to be supposition, however, what was fact, was the devastating impact of the plane into the Musi River in southern Sumatra, which tragically shattered the plane and everyone on it into unidentifiable pieces.
1 EgyptAir Flight 990, October 31, 1999 (217 fatalities)
Another highly controversial investigation where multiple countries disputed each other's findings, flight 990 was 30 minutes into its flight from New York to Cairo when it entered a rapid descent and crashed into the Atlantic Ocean.
The Captain had left the flight deck to use the restroom when the plane began a rapid descent towards the ocean, allegedly caused by the relief first officer, who was not even scheduled to be in the cockpit at that time, but had convinced his younger colleague to let him take his place for a while.
Incredibly, the Captain managed to return to the cockpit despite terrific G-forces against him, whereupon he questioned the first officer's actions regarding the flight controls and attempted to stabilise the plane by pulling back on the control column. However, the first officer does not respond to the Captain's questions and simply repeats the phrase 'I rely on God' about a dozen times, leading to speculation that he had shut off the engines and pushed the plane into a dive deliberately. There was evidence that some of the plane's control surfaces had separated from the fuselage before it impacted with the ocean due to its high speed during descent. All 217 people on board the plane were killed instantly, including high-ranking Egyptian military figures and several EgyptAir crew travelling as passengers.
It was speculated that the relief first officer had been demoted due to unacceptable behaviour while abroad on stopovers and that he was seeking his revenge on the company for the subsequent humiliation, although those findings were not altogether substantiated.