hochiman vietnamese aircraft. imagine you've just called someone on your cellphone and said i'm at "x" heading in this direction at this speed. and then you're not heard from again within the next check call. so you start to work backwards. that's how you do it. you know they were there, therefore, they were traveling in this direction at this speed and we didn't hear from them again, therefore, the search area -- now, sounds relatively straightforward when i talk about it to you on the television. we are talking about a very large space of land and water in this case, and that's why you now have navies and air forces from several countries that will be cooperating to find the wreckage of suches. and one other thing. they will be helped possibly by the underwater locator beacon. this is attached to the flight data recorder. it will be emiting a signal.