You're on a crashing plane and your partner is fast asleep. Would you wake her/him up to say 'I love you' one last time or let her/him die in her/his sleep?
The real question here is how exactly my partner is sleeping through the inevitable riot that's going to happen when the other passengers realize the plane is going to crash.
But, for the sake of answering the given question, what kind of selfish jackass would wake up someone they love in a situation like that? "Oh, hey, I'm going to wake you from your peaceful slumber that would keep you from spending your last seconds freaking out to tell you that I love you." Okay, I get the sentiment. One last chance to tell them you love them before you both potentially die. But still. That's your problem to deal with, why wake them up and have them deal with everything going on when they could die blissfully unaware?
Besides, you're most likely going to be dead soon, anyway, right? You won't care whether you said your last goodbyes.