Don't be silly.
Airliners are not designed and built to be "dive bombers," going straight down.
You're right, thought. There's not much that could stop it, other than gravity, structural strains and probable structural failure and disintegration.
Makes it impossible actually to hit the intended target.
No unidentified plane would get near enough to a Battle group to be a threat even if it was suicidal, it would be seen early on and shot down before it was anywhere near the Carrier.
Well yes, when I say straight down, I mean as straight down as a full speed 777 can do. It would still be an incredibly fast descent if done on purpose and not much could stop it given the lower profile.