Originally Posted by sailing
...Flying over populated areas on 3 rather than 4 increases the risk to people on the ground. The risk is miniscule, but it exists...
The flight is obviously not as 'safe' on 3 as on 4, but it is a minor and acceptable risk.
IMHO, the interesting topic to discuss is not the safety of this flight, it is why the FAA reacted the way it did.
The proper role of the regulatory agencies is NOT to eliminate risk (an absurdity!) NOR to bring it down to an irreducible minimum, but to specify a practical and acceptable level of safety, and the technical conditions that meet that goal. ETOPS requires a special inspection regimen, but it DOESN'T require fresh zero-time engines for every flight.
If the FAA or CAA were more stringent than what is commercially practical, we would have NO commercial aviation.