Well, if we're going to continue the parallel discussion here, then I might as well throw in a couple of cents' worth.
Final 3 Greens: What would be interesting would be to understand why the Atlantic crossing was made at FL290 - was this an ATC imposition? Its not entirely clear to me, from what I've read, whether 290 was an operational limit due to 3 engined flight.
If it was due only to ATC, why wasn't the service a little more flexible for a flight on 3?
It seems to me that this is one of the key questions. It sounds like ATC positively descended the aircraft from the original level to cross at 290, and thus turned an OK situation into one which needed re-planning.
The other key question seems to be that identified by mutt:-
mutt: 5000 kgs "appears" to be the fuel they expected to arrive in compliance with these rules.
We will have to wait to see why the MAYDAY was declared.
It seems that the aircraft actually arrived with enough fuel on board that (in retrospect) they hadn't needed to call MAYDAY, but perhaps only a PAN.
Neither of these questions suggests to me anything other than a flight which was going fine until a second curve ball was thrown, and then some sensible re-planning. The only other real question I can think of is why to MAN rather than to GLA or PIK - but again it will probably turn out that that was an entirely legitimate decision.
So I adhere to the view that, on the basis of what appears to be known, the crew did everything by the book at the time the decision to press on, and there appears to have been no safety reason for a return to LAX at that time. And as we all know, there are added risks and environmental damage involved in such a return, before you get to commercial considerations.
strake: This incident however seems to be different. It was not an immediate emergency. However, a pretty important piece of the aeroplane stopped working. In a p*****g competition between "Professionals" and "Public Opinion", the latter will ALWAYS win. I think (imho) if 100 experienced travelling PAX were asked what they would prefer in this situation, the majority would say "land".
Which is why it is such a good thing that airliners are not operated by the popular vote of uninformed pax. If my fellow pax had to decide when we were and weren't going anywhere, I suspect that I'd only get about half of my trips completed as booked.
Let's face it, if given the choice between a riskier return to origin and a safer three-engine continuation, which would you choose?