It confirmed that, after the jet took off from Austin, the crew transmitted to air traffic control that they were encountering ice and moderate turbulence.
“We are picking up precipitation, requesting to climb to 37,000 feet if able,” the crew said.
NTSB member Tom Chapman said that less than 30 seconds later, the plane began to descend and the crew issued a mayday call.
The transmission then became “unintelligible”, he said, adding that: “Sadly, all aboard were lost.”
The NTSB said that ice and turbulence were factors in the crash but that determining its probable cause will be a “lengthy investigatory process”.
Thunderstorms had been reported in the area at the time.
Officials are also trying to find out whether a cockpit voice recorder was on board at the time of the crash and if it can be recovered.
As part of the investigation, the NTSB is working with the Federal Aviation Administration (FAA), representatives from Learjet as well as meteorologists and air traffic control experts.
Recovering the wreckage from the crater on the roadway will be a “daunting challenge”, said Timothy Monville, an air safety investigator with the safety board.













