A team from the National Transportation Safety Board is collecting the last of the wreckage from a hot air balloon that plummeted into a sun-scorched Texas pasture in a crash that killed 16 people.
But the investigation into the deadliest hot air ballooning accident in modern U.S. history is just beginning. Here's a look at what lies ahead in the case of the balloon that hit power lines and caught fire Saturday southeast of Austin.
WHAT DO WE KNOW?
The NTSB found "no evidence of pre-existing failures, malfunctions or problems" with the Czech-made Kubicek-brand balloon. The balloon's top vent was open at the time of the crash, suggesting pilot Alfred "Skip" Nichols was trying to land, the board said.
The balloon was designed to carry up to 4,400 pounds, probably plenty for Nichols and his 15 passengers. Alan Lirette, who was Nichols' roommate and helped launch the balloon, said it was designed to take up to 16 passengers plus the pilot, meaning it was not full.
Except for reports of patchy fog in low-lying areas, the weather was believed to be clear just after sunrise when the balloon lifted off.
WHAT DON'T WE KNOW?
Investigators don't know why the balloon flew into electric wires about 140 feet above the ground. Inspection crews found evidence that the balloon made contact with the wires for about 30 feet. But they can't yet say when the flames broke out that engulfed the basket carrying everyone aboard.
The FBI found 14 personal communication devices, including cellphones, at the crash site. They recovered three cameras and an iPad that Nichols used to navigate the balloon. All of the devices are believed to have been destroyed, but an NTSB lab will try to salvage any surviving information.
The NTSB expects to produce a report on the accident, but that will probably take months. The company that owned the balloon, Heart of Texas Balloon Rides, has suspended operations. The Texas secretary of state said the company never registered with state officials but that it did not necessarily have to.
The crash victims' remains have been taken to Lockhart, a town near the crash site known mostly for its barbeque. There Dr. Suzanna Dana is expected to perform autopsies. She has declined to comment.
Medical examiners elsewhere say traces of air-crash victims' remains can be sent to federal labs that perform a variety of tests, including screening pilots for alcohol, but authorities have not said if that will occur this time.
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Such tests could be important since Nichols was allowed to keep flying despite at least four drunken-driving convictions. His former girlfriend, Wendy Bartch, said he was a recovering alcoholic who had been sober for at least four years.
WHAT DO REGULATIONS SAY?
A drunken-driving conviction that occurs within three years of a previous conviction is grounds for suspension or revocation of a pilot's license, according to the Federal Aviation Administration, which oversees hot air balloon regulations.
Nichols obtained his hot air balloon pilot's license in Missouri in 1996, went to jail on a drug charge in 2000 and was last convicted of drunken driving in 2010.
The NTSB has long pressed the FAA for stricter hot air balloon oversight.
In a 2014 letter, the board urged the adoption of a requirement that tour companies get FAA permission to operate. The board also wanted to make balloon operators subject to safety inspections, writing: "The potential for a high number of fatalities in a single air tour balloon accident is of particular concern."
The FAA said those regulations were unnecessary because balloon risks were too low.
But Philip Bryant, a suburban Houston balloonist who performs manufacturer-mandated inspections of hot air balloons, is worried that the federal government may now react to Saturday's crash by severely tightening regulations more for show than to improve safety.
"Frankly," Bryant said, "I fear retribution from the FAA."