This is second hand information I was told by my work associate. On August 18 2016 around 4 to 5 PM in Lewistown Illinois she and other family members heard very loud jet engine noise and thought a plane was going to crash into her home. The engine sounded strong then struggling. She went outside and only saw a contrail that was in a straight line then dropped down then sharply angled upward trailing off in a few spirals. She said it looked like a huge check mark in the sky. Never saw a plane and the neighbors were out looking also.