NTSB says crucial plane parts found three miles from Florida crash site

"Knowing that it was lost is a very important piece of evidence in terms of pointing us towards other things to investigate," he said.

Chapman said officials were still working out whether losing the left elevator caused the plane to nosedive or whether the part fell off because "forces on the aircraft caused that to separate".

He said the part of the plane that controls upward and downward movement may not have been "effective" at the speed the plane was travelling.

The Learjet 60 was bound for the Bahamas from Austin, Texas, when it nosedived into a multi-lane highway and exploded on impact.