I think they meant “hiding it” by crashing the aircraft if a very remote, deep and mountainous part of the ocean. The Titanic was relatively easy to find, flat ocean floor. Try finding it in an underwater mountain rage.

Also, it is going somewhere. Currents can move it around and spread it out. That is why they find a piece every so often washed up somewhere. It would take some Star Trek level sensors to find this thing now.