The National Transportation Safety Board said on Saturday that the pilot of the American Airlines plane that collided with a Black Hawk helicopter earlier this week may have witnessed the incoming danger and tried to move the plane upward to avoid the crash.

American Airlines CEO Robert Isom said the National Transportation Safety Board, which is investigating the deadly midair collision between an American passenger jet and a military helicopter, will be the lone authority on the cause and details of the crash.

There are confirmed fatalities from the collision of American Airlines Flight 5342 and the U.S. Army Black Hawk helicopter over the Potomac River. Several bodies have been pulled from the Potomac River crash site, according to two law enforcement sources familiar with the ongoing operation.