http://www.thelocal.fr/20111125/1869
This plane took off with 30 screws missing. But if it was under critical moment (extreme weather or mechanical failure), going with 30 screws could have a chain impact and eventually lead to a fatal crash.
http://www.huffingtonpost.com/2013/10/13/door-falls-off-plan...
This is another lucky incident at 1000 feet. Imagine this at critical moment and at 20k, 30k altitude! I would suppose some passengers would die if that happened.
Remember, you're far, far more likely to be injured or killed driving a car than taking a plane. It's one of - if not the - safest form of transport out there.
I think that's up to argument and depends on how one look at the issue. Is plan safer? There are more corners, more cars, more trains than aircraft combined at any given time. And the most important thing to consider is getting help. I have to press hard on this: if you are in the air, the chance of you surviving is low. Even on the ground after a serious car accident at a reasonable location, most patients could receive proper medical treatment within minutes. But when you are in the air? In the case of gunman I could try to escape on the ground but not really in the air.