Originally Posted by
Sailvi767
You are not required nor is it desirable to use single engine long range cruise in a engine out ETOPS situation. In most ETOPS diverts the issue is going to be high gross weight landing due to having to much fuel onboard.
Except the exceptional case relating to the Airworthiness Directive for the 787, with RR Trent 1000 pack C engines, with either engine >300 cycles requires it. See the FAA AD can be seen
here. The requirement is stated on page 7