Originally Posted by alanh
Anyway, I don't know of any all engines out failure on a twin that would have been helped by an extra engine or two.
Here's a little bit of reading that you might find enlightening:
4 March 2001; United Air Lines 767; near Kona, HI: While early reports indicated that this 767 had a complete loss of power in both engines, the analysis of the flight data recorder by the NTSB does not support this conclusion. According to early FAA and media reports, United Flight 42 took off from Kahului on the Hawaiian island of Maui on a flight to Los Angeles and experienced a dual-engine shutdown about 70 miles (112 km) into the flight, followed by an in-flight restart and a diversion to the Kona airport. Later analysis of the flight data recorder by the NTSB showed that both engines had a reduction of power to below idle, but did not show any evidence of a complete loss of power in either engine. However, there was roughly a 30-second gap in the data during the time when the engines were operating at reduced power. The aircraft, registration number N666UA, has since been returned to service.
Other 767 aircraft have experienced dual engine shutdowns on at least five other occasions:
23 July 1983; Air Canada 767; near Gimli, Manitoba: The aircraft ran out of fuel after the crew miscalculated the weight of fuel on board. The aircraft made an emergency landing on an abandoned airfield. There were no serious injuries.
19 August 1983; United Air Lines 767-200; near Denver, CO: Fuel contamination led to a dual-engine shutdown at about 41,000 feet. The crew restarted the engines at about 15,000 feet.
31 March 1986; United Air Lines 767-200; San Francisco, CA: The engines were inadvertently deactivated the engines during climb at about 3,000 feet. The crew was able to restart the engines and returned to the departure airport.
30 June 1987; Delta Air Lines 767-200; Los Angeles, CA: The engines were inadvertently shut off during climb at about 2,000 feet. The crew was able to restart the engines at about 500 feet and continued to their original destination of Cincinnati.
23 November 1996; Ethiopian Airlines 767-200ER; near Moroni, Comoros Islands: The aircraft was on a flight from Ethiopia to Kenya when it was hijacked. The hijackers refused to allow the aircraft to refuel, leading to a dual engine shutdown due to fuel exhaustion. Ten of the 12 crew members and 117 of the 160 passengers were killed during a subsequent ditching. The three hijackers apparently died.