Flying to the USA from Australia via NZ in 1992. About half way across the pacific a weird engine noise came across. A minute later the pilot come on and says "Folks, I don't want you to be alarmed by the noise you might have just heard, but we're having a problem with engine number 3 and we've had to shut it down as a precaution". Didn't stress. About 30 minutes later a similar weird noise happens... then the pilot announces "Folks, so sorry to do this to you but we're having a problem with engine 1 now and as a precaution, we've shut it down. There's nothing to worry about though, these planes are designed to be able to fly on just one engine." So we're operating at 2/4 engines and about in the middle of the Pacific ocean and I attempt to get some more sleep. 2hrs later... a third weird engine noise happens and again, the pilot comes over the PA "Folks, terribly sorry about this but we're now down to just the one engine. But don't worry, air traffic control are fully aware of our situation and we're only about 2 hours out of LA at this point, we'll be fine."

... that's when the turbulence started.