[1] On 2 September 1998, the McDonnell Douglas MD-11 performing this flight, registration HB-IWF, crashed into the Atlantic Ocean southwest of Halifax Stanfield International Airport at the entrance to St. Margarets Bay, Nova Scotia, Canada.

The search and rescue response, crash recovery operation and investigation by the government of Canada took more than four years and cost CA$57 million.

All crew members on board Flight 111 were qualified, certified, and trained in accordance with Swiss regulations under the Joint Aviation Authorities (JAA).

[7] At 22:10 ADT (01:10 UTC, 52 minutes after takeoff), while flying over Yarmouth, Nova Scotia, the flight crew detected an odour in the cockpit and determined it to be smoke from the air conditioning system.

Halifax thus vectored the plane south toward St. Margaret's Bay,[3]: 2–3  where it was safe for the aircraft to dump fuel while remaining within 40 nautical miles (45 mi; 75 km) of the airport.

With Captain Zimmermann likely dead or incapacitated by fire and smoke, in a smoke-filled cockpit, and with almost no flight instruments and little to no view outside, it is possible that Löw became spatially disoriented and as a result, flew into the sea.

Another possibility is that while attempting to see outside the cockpit windows, Löw inadvertently pushed the control column forward, thus resulting in a descent and eventual impact with the water.

[10] There were 132 Americans (including one employee each from Delta Air Lines and United Airlines), 41 Swiss (including the 13 crew members), 30 French, 3 British, 4 Canadian, 3 Italian, 2 Greek, 2 Lebanese, 1 each from Afghanistan, China, Germany, India, Iran, Russia, Saudi Arabia, Spain, St. Kitts and Nevis,[11] Mexico, Sweden and Yugoslavia, and 4 other passengers on board.

[18][19] Swiss tennis player Marc Rosset had originally booked a ticket home for the flight, but cancelled the day prior to practice further after losing a match in the US Open.

[21] Local fishermen and boaters, many of whom were CCGA volunteers, were the first rescue resources to approach the crash site,[21] which were mostly privately owned fishing boats operating from Peggy's Cove and Bayswater, as well as other harbours on St. Margaret's Bay and the Aspotogan Peninsula.

An EHS helicopter was also sent to the crash site, and the Queen Elizabeth II Health Sciences Centre in Halifax was put on emergency alert.

[29] On the morning of 4 September, JRCC Halifax de-tasked dedicated SAR assets and the Transportation Safety Board of Canada (TSB) were given control of the scene.

Additionally, the USS Grapple welcomed two teams of Canadian Navy Clearance Divers that flew across Canada from Fleet Diving Unit (FDU) Pacific.

[34] On 2 October 1998, the TSB initiated a heavy lift operation to retrieve the major portion of the wreckage from the deep water before the expected winter storms began.

[36] Jerome Hauer, the head of the emergency management task force of New York City, praised the swift actions of Swissair and codeshare partner Delta Air Lines in responding to the accident; he had criticized Trans World Airlines in its response to the TWA Flight 800 crash in 1996.

Based on internal TSB summaries of the CVR recording, the Journal claimed that co-pilot Löw suggested steps aimed at a quick landing, which were ignored or rejected by Captain Zimmermann.

[3]: 253  After the crew cut power to "non-essential" cabin systems, a reverse flow in the cockpit ventilation ducts increased the amount of smoke reaching the flight deck.

[3]: 254 The rapid spread of electrical power failures led to the breakdown of key avionics systems, and the crew was soon rendered unable to control the aircraft.

Recovered fragments of the plane show that the temperature inside the cockpit became so great that aluminium parts in the flight deck ceiling had melted.

[3]: 104 Both first and business class seats were equipped with a Windows NT 4.0 based In-Flight Entertainment Network (IFEN) system with touchscreen in-seat video displays and magnetic card readers.

[3] In the galley, a cabin file server served as a central hub for managing content, which facilitated movie downloads, stored flight and casino information, and collected credit card data transmitted from each seat.

As a result, 115-volt three-phase 400 Hz AC Bus 2, located in the cockpit area (the origin of the fire), was used to provide most of the IFEN power requirements.

Andromidas further alleged that a key Swissair safety official involved in the investigation, upon returning to Switzerland, was banned from speaking to the press and even his superiors.

Andromidas followed up with a subsequent article on November 13th, mentioning that Swiss daily Neue Zürcher Zeitung had reported a burglary at Swissair headquarters in Zürich, occurring about a month after the crash.

[65] Further, Juby claims he was asked by senior RCMP officials to retroactively edit his notes for the public record of the investigation so as to omit any mention of his views on the plausibility of an incendiary device having brought down the flight.

[69][70] In a 2023 interview with Swiss daily newspaper Tages-Anzeiger, German aviation journalist and commentator Jens Flottau believes it would have been advantageous had the pilots decided to land directly without dumping upon smelling smoke.

The company applied for a treasure-trove license from the Nova Scotia government to search the crash site but faced opposition from victims' relatives, leading to the withdrawal of the application.

Halifax-based TV documentary producer John Wesley Chisholm suggested that treasure hunters might have covertly explored the area in the years following the crash.

[79] In September 1999, Swissair, Delta Air Lines, and Boeing (who had acquired McDonnell Douglas through a merger in 1997) agreed to share liability for the accident and offered the families of the passengers financial compensation.

Among those in attendance were 175 relatives of the crash victims, Swiss president Flavio Cotti, Canadian prime minister Jean Chrétien, and Nova Scotia premier Russell MacLellan.