Seriously though, this movie sucks.  
There are no redeeming qualities about it, it sucks. If you want to see how not to do a book-to-movie adaptation go no further because this movie has perfected it to a tee. The book is about how the human world would survive after a zombie apocalypse, and for what is worth there is not a single zombie in it since it deals with the aftermath. The movie is a mindless action fest with hordes of zombies piling onto each other and they move like water.  
Oh, and they detonate a grenade inside a plane and survive. How do you-what!?  
This movie sucks. Avoid it like the plague.