Downeast Flight 46 crashes on approach to Knox County Regional Airport in Rockland, Maine, killing 17.

Downeast Airlines Flight 46 was a scheduled airline service in the United States from Boston's Logan International Airport to Rockland, Maine operated by Downeast Airlines. On May 30, 1979, the de Havilland Canada DHC-6 Twin Otter operating the flight crashed during a nonprecision approach to Rockland's Knox County Regional Airport. All but one of the 18 people on board were killed. The cause of the accident was controlled flight into terrain (CFIT) after the failure of the flight crew to stop the aircraft's descent below the minimum descent altitude for the non-precision approach at Knox County airport. The investigation into the accident looked into the airline's corporate culture as a contributing factor to the crash; this was the first time an investigation took this approach to an air crash.

Knox County Regional Airport is a county-owned, public-use airport in the town of Owls Head, Knox County, Maine, United States. It is located three nautical miles (6 km) south of the central business district of Rockland, Maine. The airport serves the residents of midcoast Maine with commercial and charter aviation services. Scheduled airline service is subsidized by the Essential Air Service program. It is also a major hub of freight and mail service to Maine's island communities including Matinicus, North Haven and Vinalhaven.

Rockland is a city in and the county seat of Knox County, Maine, United States. As of the 2020 census, the town population was 6,936. The city is a popular tourist destination. It is a departure point for the Maine State Ferry Service to the islands of Penobscot Bay: Vinalhaven, North Haven and Matinicus.

May 30 is the 150th day of the year in the Gregorian calendar; 215 days remain until the end of the year.