I disagree with those who think that the emergency should have been downgraded. The loss of one engine on a twin-jet public transport aircraft certainly warrants a mayday. What advantage would be gained by then downgrading? Remaining on a mayday keeps ATC focussed (and hopefully quiet) and everyone else out of the way. On my current type if I lose 50% of installed thrust I will declare and maintain a mayday, notwithstanding that in such circumstances I have the added luxury of still having 2 engines running.