The leader of NASA is standing up against online criticism of the copilot in the Learjet 60 private plane that crashed in South Florida on Sunday.

Jared Isaacman, the NASA administrator who is also a pilot, said he was speaking out in a personal capacity to address some of the reactions to the crash, which killed nine people. Authorities have not said what caused the crash, and the identities of the pilots and the passengers have not been released, but a recording of a female copilot's mayday calls in the moments preceding the crash sparked reactions online.

"I feel compelled to post after seeing commentary about the Lear 60 crash, from missile strikes to DEI to critiquing this poor woman's final radio calls," Isaacman wrote in an X post on Monday. "That last part is what I find most troubling."

"She was the second-in-command (SIC), and while she was empowered to point out mistakes as part of good crew resource management, she was doing her job, communicating with ATC right to the end in a terrifying situation. She likely knew before many of those calls that she was going to die," he continued.

Isaacman said he understood the public interest but that many factors remained unknown, including "the aircraft's maintenance history, whether there was a structural failure, if any failure was induced by turbulence, overspeed, or overcontrol, or everything happening in that cockpit."

He also said that the charter industry often hires early-career commercial pilots who need to gain experience alongside airline-qualified pilots, adding the copilot would still have the necessary training and qualifications.

"Let people investigate, learn, and share the facts. Be respectful to those who perished and the families who carry their memories," he added.

The plane had departed from Austin and was en route to the Bahamas when it entered Florida on Sunday. It descended 27,000 feet in about a minute before crashing into the ground, data from FlightRadar24 showed.

Officials from the National Transportation Safety Board have said that weather is a major focus of the investigation into the crash. South Florida experienced widespread thunderstorms on Sunday, with aviation weather data showing heavy rain, low visibility, and moderate turbulence.

Mark Stephens, a retired Delta Air Lines pilot, told Business Insider that weather could have played a role and warned against jumping to place blame on the pilots.

"Everybody's jumping to conclusions about the pilot; it's like Monday morning quarterbacking. 'Oh, it's her fault,'" Stephens said. "Well, that's a load of crap. And she wasn't even the captain."