They're not required or expected to. This is a motivation we had ourselves; we went out and sought this. There are a lot of airports in the U.S. that have that certification. It is a U.S.-based organization. Back in 2001-02 we started the steps to try to make our systems more rigorous, and just as for an ISO certification, we went into the process of documenting our processes and plans in order to retain that certification. I can also say that we've gone back every two years to be recertified, and we have been certified again.
We thought it was a very good process, a very thorough one that went into all levels of the security aspect of the airport, including and especially the preparation of standards, the preparation of emergency plans, the training of our people, and a whole myriad of other things.
But it was at our initiative; it was not a requirement.