1. Underneath means in a lower position than something else.
The sheets are underneath the blankets on the shelf.

2. Underneath means covered by.
I found my jacket underneath the other coats.

3. Underneath indicates concealed feelings.
Underneath her smile there is a lot of heartache.
He is really very kind underneath his stern appearance.

Myth about Airplanes

Open all the windows during takeoff and landing

Having the window open allows a passenger to see what s going on outside in a split second and it s not only because the window is opened. Say imagine if the plane crashes and the windows then just automatically open on its own leading way to a ray of bright sunlight coming into the passenger cabin. For a few seconds, all the passengers inside won t be able to see anything outside until their eyes adjust to the bright sunlight outside. That few seconds in the case of an emergency is crucial.