In the United States, the National Transportation Safety Board has evidence that the Learjet 60 that crashed in Palm Beach County, Florida, on Sunday 1 November began to break up before impact. NTSB Member Tom Chapman said so at a media briefing in West Palm Beach on Monday. "We're still seeking to determine that," he added12. Chapman also confirmed the operator: Aurora Aviation, with the flight conducted under Part 135, the US rules that cover commercial charter flights among other operations1. We reported earlier on the crash itself and on the radio calls and ice at FL350.

Listen to the ATC audio of N722BD with Miami Center, with a timeline and quotes.

The final minutes according to the NTSB

Chapman gave a first timeline at the briefing, in local time (EST, UTC minus 5 hours)1:

• At about 10:37 the aircraft left Austin-Bergstrom International for North Eleuthera in the Bahamas with nine people on board: two flight crew and seven passengers1.
• At about 12:47 the crew reported light, clear ice that was manageable and moderate turbulence. To Miami Air Route Traffic Control Center they reported being at 35,000 feet with altitude deviations of about 700 feet and an outside air temperature of minus 47 degrees Celsius1.
• Soon afterwards the crew reported picking up precipitation and asked to climb to 37,000 feet. FAA air traffic control approved the request1.
• Less than 30 seconds later a transmission from the aircraft announced a descent, followed by a mayday1.
• At about 12:48 came "we are in an overspeed condition descending", with the rest of the call unintelligible. Later calls said the aircraft was descending rapidly and gave an altitude1.
• The crash followed at about 12:51, according to the NTSB1.

That fits the ADS-B data published by Flightradar24: at 17:48:07 UTC, 12:48 in Florida, the aircraft transmitted 35,250 feet, and the last altitude value was 8,750 feet at 17:49:22 UTC3.

Breakup in flight and a wide debris field

"We do have some evidence that there was some breakup of the aircraft before impact," Chapman said1. The NTSB therefore expects to find parts some distance from the impact site. Which parts these are has not yet been established, and Chapman would not yet comment on the tail1.

The debris field is about half a mile by four tenths of a mile, roughly 800 by 640 metres, according to the investigator in charge. Most of the debris is small and is scattered across ball fields, businesses and homes1. The biggest obstacle, according to the NTSB, is recovering the main wreckage from the crater in the road, which has water in it1. On the speed at impact Chapman would only say that it was high; there are no precise figures yet1.

Cockpit voice recorder likely installed

Maintenance records indicate that a cockpit voice recorder was installed in the aircraft, Chapman said. Whether it was still on board for this flight is not yet known1. "We'll be better off with it," he said, adding that investigators can still reconstruct how the accident unfolded without it1.

Weather at 35,000 feet is a focus

Asked whether the ice and turbulence played a part, Chapman replied: "That's certainly a factor, absolutely"1. Weather is a major focus of the investigation, but conditions at 35,000 feet still have to be determined1. The NTSB cannot yet confirm whether the aircraft flew through an active thunderstorm1. Investigators are also looking at who knew what and when, what actions were taken and whether they were appropriate, and whether a heading change came from ATC or from the crew1.

Chapman said he had no indication of a history of this type of accident with the Learjet 60. The NTSB will look for trends with the type and at this aircraft's own history1. What the FAA says about ice at minus 47 degrees is covered in our report on the radio calls.

The investigation team

About 20 NTSB investigators began arriving on Sunday evening, with more staff following on Monday1. The investigator in charge, a senior investigator with nearly 40 years of experience, reached the site at about 7 p.m. on Sunday1. His team includes a drone pilot, systems and structures specialists, a recorder specialist and staff from the Office of Transportation Disaster Assistance1. The FAA and representatives of the manufacturer Learjet Inc. are assisting, possibly joined by the operator. Weather and air traffic control specialists are working off site1.

On scene work will take several days, and the NTSB will not determine a probable cause while there1. The NTSB asks witnesses with video or other information to email witness@ntsb.gov and asks residents not to move any debris they find1.

An injury on the ground

Governor Ron DeSantis said on Sunday that there were no reports of deaths or injuries on the ground4. According to the investigator in charge, a man in a vehicle leaving the area right next to the impact site suffered a leg injury1. How serious it is was not yet known on Monday1.

The NTSB does not release the names of those on board; Chapman said they will come from local authorities1. According to her family, the co-pilot was Nathalia Gadelha Filgueiras, 2056. According to their family, Adam Robinson and Helen Sharp were also on board with their two young children78. The names of the others on board have not been released. He could not yet say when the roughly 600 evacuated residents can return14. Everything established so far is collected in the dossier on Learjet 60 N722BD.