These flights happen many times every day!
Think 757, 777, 767.... I for one have flown over the Atlantic in all three ( I think) and so far have not gone plumeting to the ocean bed...
There is a thing where people think that 4 engines is the only safe way over ocean routes... maybe this is because of Virgins slogan:
"4 engines 4 longhaul" or whatever it is...
Well even they have gone against what they preach and have placed an order for the new 787s!
And guess what... they are two engined beasts =)
If your worried you could wear the life jacket throughout the flight.... at least you would get attention from the hostess
But seriously it will be fine!
(but i do always check that my lifejacket is there and in place by having a quick feel! - anybody else do this or do they just pressume that everyone have done their job...?)