I'm fairly sure that the decision would have been made with the help/ consultation of their engineering department. By that I mean the engineering department would have been receiving real time data on the health of the aircraft, this is usually a lot more detailed than what is presented to the pilots.
In 40 years I've never had an engine failure and may it be so for the next couple before I call it a day. If after ticking all the boxes, I would also continue on 3 engines if I thought it were safe.
Last edited by Offchocks; 11th Nov 2013 at 21:19.