Yes, that's a very good question.
Aviation security is always explained in terms of having different layers. There are several layers that already exist. As you quite rightly point out, you're screened before you get on the airplane. Your baggage is checked. In addition, there's already a program that provides that information is provided to American authorities if you're landing in a city in the United States. The secure flight program is layered on top of that.
It's a fair question to ask whether this additional layer will add any additional security. But as Commissioner Stoddart has pointed out, it's difficult for us to make the judgment about whether this new layer is providing any additional security. The American government believes that it will provide additional security. It's not readily apparent what that would be, but we're not aviation experts.