What Is The Worst Airplane Crash In US History?

The Tenerife airport disaster was the collision of two Boeing 747 airliners on the runway of Los Rodeos Airport (now known as Tenerife North Airport) on the Spanish island of Tenerife, one of the Canary Islands.
With 583 fatalities, the crash remains the worst accident in aviation
history, and the second-worst air disaster of any kind (after the September 11 terrorist attacks in 2001).
The collision took place on March 27, 1977, at 17:06:56 local time. The aircraft involved were the 747s of Pan Am Flight 1736 (the Clipper Victor) under the command of Captain Victor Grubbs, and KLM Flight 4805 (the Rijn) under the command of Captain Jacob Veldhuyzen van Zanten. Taking off on the airport's only runway, the KLM flight crashed into the Pan Am aircraft taxiing on the runway in the opposite direction.

The worst airplane crash in United States history occured on May 25, 1979 when flight 191 left from O'Hare Airport . The plane was an American Airline and occurred at 3:02 PM, about thrity seconds after take off. Upon take off, the engine on the port side of the plane fell off, the plane fell from 400 feet and about a half of mile from the runway. The plane exploded on impact, killing everyone aboard and 3 additional people who were on the ground. Approximately 271 people were aboard the plane.  It was later determined American Airlines were not following the McDonnell Douglas procedures for removing engine pylons for maintenance (nor were they required to). McDonnell Douglas' instructions involved removing the 13,500 pound engines from the pylons (which hold the engines on the wing) and then removing the nearly 2,000 pound pylons.