I'm grateful that this is a rare type of accident but it has happened before.

http://www.crashdatabase.com

Date: 03/31/1993
Location: Anchorage, Alaska
Airline: Japan Airlines (Operated by Evergreen
International)
Aircraft: Boeing 747-100
Registration: N47EV
Fatalities/No. Aboard: 0:5
Details: The No.2 engine and pylon separated from the aircraft at 2,000 feet. The plane landed safely. The engine separation was due to an encounter with severe or possibly extreme turbulence and a fatigue crack.

Date: 10/04/1992
Location: Amsterdam, Netherlands
Airline: El Al Israel
Aircraft: Boeing 747-200F
Registration: 4X-AXG
Fatalities/No. Aboard: 4:4 +47
Details: Shortly after taking off from Schiphol Airport, while climbing through 6,500 feet, the No. 3 engine separated with its pylon from the aircraft and damaged the leading edge of the right wing. The No. 3 engine separated in such a way that the No. 4 engine and pylon also separated from the wing. During an attempted return to the airport, the aircraft crashed into a 11 story building in the Bijlmermeer residential district. The design and certification of the B-747 pylon was found to be inadequate to provide the required level of safety. The system to ensure structural integrity by inspection
failed. The separation of the No. 3 engine was initiated by fatigue (corrosion) in the inboard midspar fuse pin. This led to loss of the No. 4 engine and pylon and damage to several systems which ultimately led to loss of
control of the aircraft.

Date: 01/18/1988
Location: Chungking, Sichuan, China
Airline: China Southwest Airlines
Aircraft: Ilyushin Il-18D
Registration: B-222
Fatalities/No. Aboard: 108:108
Details: The aircraft crashed 10 minutes before its scheduled landing. Fire in and failure of the No. 4 engine led to separation of the pylon and engine and loss of control of the aircraft. Overheating of the feathering oil. Poor maintenance procedures.

Date: 05/25/1979
Location: Chicago O'Hare, Illinois
Airline: American Airlines
Aircraft: McDonnell Douglas DC-10-10
Registration: N110AA
Fatalities/No. Aboard: 271:271 +2
Details: During takeoff just, as the plane lifted from the runway, the left engine and pylon separated from the aircraft damaging the wing and hydraulic system which caused the aircraft to roll and crash. Highest single plane death toll in U.S. aviation history. Asymmetrical
stall and the ensuing roll of the aircraft because of the uncommanded retraction of the left wing outboard leading edge slats and the loss of stall warning and slat disagreement indication systems caused by separation of the engine and pylon. Improper maintenance procedures
used by American Airlines when dismounting the engines for maintenance, putting strain on the engine mounts.