What isn't so clear is how a trait that is primarily used to save yourself from violent death gets lost to someone else if you happen to bleed on someone in the process of dying violently. Which would seem to be a not very rare occurrence.
It's also not clear how the mechanism of stealing works. You get doused in Alpha blood, which kills you, but also at the same time gives you their powers, and when you jump back in time the blood comes with you.
So after that the Alphas want to kill you and get the power back. They can tell they've lost the power, and i guess they can tell which human ended up with it because they get linked into the hive mind thing? So they start sending telepathic messages to the human to lure them to a place where an Alpha can ambush them and get the power back. Okay, fine, i can roll with that.
And given the assumption that the alien blood travels back in time with them, i can also roll with the idea that getting a transfusion causes you to lose the power.
However if the human loses the power, how do the aliens get it back? It seems like the power is a kind of metaphysical object that only one person/species can possess at a time. If a human gets alien blood they somehow overpower the alien's ability to use the power (because we never saw him snap back without getting killed himself, despite at least one Alpha being in combat during the beach assault) but as soon as the human loses the power it magically reverts back to the aliens even without a transference of blood.
And speaking of the Alpha on the beach, why did they set up a trap for him at the dam when there was already an Alpha in position on the beach to take him out?
And i am curious what would have happen if someone else had killed the Alpha and gotten doused in blood while Cruise was running around elsewhere in the beach. Would that person have stolen the power from Cruise? Or would time have gotten reset for whichever of them died first in the day? And if so, would the person who hadn't actually died remember it?
I did appreciate how Rose was willing to shoot Cruise early and often, given that there was pretty much no penalty for doing so and always the potential of something going wrong later. However as they were making their escape from the government building with the "find the aliens" device, as soon as he used it and got the image i was thinking "okay, quick, shoot him now." It's understandable however that she was kind of caught up in the moment of trying to escape, and didn't really have time to think about stopping to shoot him before they got caught.
I did wonder a bit about why Rose, an international hero who clearly was granted all kinds of perks because of her celebrity, couldn't commandeer a drop ship for a "deep strike" mission to the dam. It's true she wouldn't have been able to explain exactly why, but you'd think she could have made something up, and it's not like she would have been requesting not to go into combat at all. Of course the biggest reason for that not being viable of course would have been that it would have screwed up the plot.
I'm kind of annoyed by the kiss near the end. Yeah, everyone was expecting it, but it would have been nice if they'd left the imminent relationship implied rather than explicit, kind of like Pacific Rim.
So my big gripe, i was expecting that Cruise would get doused with Alpha or Omega blood and be able to rollback the deaths of everyone. It would have been an interesting movie if everyone had sacrificed themselves to save the rest of the human race, but i wasn't expecting that from a blockbuster movie.
It's entirely reasonable that the Omega's blood had the same power as the Alpha's blood and could be absorbed by Cruise the same way. (In fact, does that mean if Cruise hadn't been close enough to absorb the blood and steal the power that the Omega itself would have time looped back and all would have been lost?) It's also fair that the Omega's blood is more powerful than the Alpha's and thus sends him back further than the Alpha blood did.
However if Cruise time looped back, why was the Omega still dead when that happened? That part makes no sense to me.
Hmm, but if the claim is that when you steal an alien's time traveling power it retroactively dies at the start of the loop, that would explain why we never saw the Alpha on the beach again.
It seems a little unfortunate that Cruise got looped back to before the invasion happened with the Omega already dead. Ye he's saved Rose and all his "friends", not to mention the human race, but he's not going to get any credit for it, and aside from Rose none of his comrades-in-arms will believe they knew him and helped save the world.
Also, presumably Cruise still has the time loop power? If he makes it through about 48 hours does the "checkpoint" get advanced? Or will he always jump back to that moment in the helicopter? If so, how many loops will he do before getting sick of it and getting a transfusion. If the jump is always to "the point where you woke up closest to X hours before you died", how will he make use of that? Winning the lottery sounds like a good start.