The same people who shot Kennedy hide the plane. You will be disintegrated in 3 minutes.<p>Or you could use the grey matter between your ears. Modern airliner hulls and structure are made mostly out of aluminium, which is -suprise- antimagnetic.<p>And finding a Submarine or anything else is hard. Like really hard. You need to know where to look. Because of that, NATO would have to had stopped Red Fleet at the GIUK-Barrier or it would have gotten ugly. 
Or, look at the problems people had to find ships like Titanic or Bismarck, where they had much more precise locations to start searching for.