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.

In air traffic control audio recordings, someone in the cockpit can be heard reporting "moderate turbulence" and that the crew was "managing the ice".

They are then heard saying the plane was "picking up precipitation" and "we need to climb". Moments later, the same voice said the plane was descending at a rate of 10,000ft (3,048m) per minute.

An emergency was declared and the pilots can be heard yelling "we are in an overspeed condition descending 20,000ft per minute", before saying, "we are going to crash into the ground".

NTSB plans to investigate the role weather played in the crash. Officials were struggling to access the wreckage due to the huge crater created by the jet on a road in Palm Beach.

Chapman said on Tuesday that the force of the impact severely damaged the wreckage.

Seven passengers died on board, named in a joint statement as tech entrepreneur Adam Robinson, his wife, Helen Sharp, and their two children - Emma, four, and Charlie, two - as well as friends of the family Rachael Reed and Charmi Fehr, and Anita Maria Cetina, a nanny.

The pilot was named in media reports as 55-year-old Jeffrey Gregory. Nathalia Filgueiras, 20, who earned her pilot's licence when she was 17, was reported to be the co-pilot.