Newton's 3rd Law
“ Lex III: Actioni contrariam semper et æqualem esse reactionem: sive corporum duorum actiones in se mutuo semper esse æquales et in partes contrarias dirigi. ”
“ Law III: To every action there is always an equal and opposite reaction: or the forces of two bodies on each other are always equal and are directed in opposite directions. ”
There's nothing stupid about being perplexed when witnessing what is supposed to be a plane flying inside a building. If anything, you are being the stupid one, in thinking that a plane would do anything other than bounce off the building.