Star Wars actress Carrie Fisher is in intensive care after suffering a mid-air medical emergency.
Her brother, Todd Fisher, told The Associated Press that she was "out of emergency" and being cared for at a Los Angeles hospital.
"It's not fair to say 'stable.' I am not saying she is fine, or not fine," he said. "She is in the ICU (intensive care)."
Fisher reportedly went into cardiac arrest about 15 minutes before Flight 935 from London to Los Angeles landed around noon on Friday. She was administered CPR while aboard the aircraft, TMZ reported.
A source who said they were not authorised to discuss the incident said the actress was "in a lot of distress on the flight".
Fisher, who rose to stardom as Princess Leia, recently published an autobiography titled the Princess Diarist, her eighth book.
She had been in London promoting the book and also shooting the third season of the British television comedy Catastrophe.
United Airlines issued a statement saying the flight was met on the ground by medical personnel after the crew reported that a passenger was "unresponsive," but the airline did not name the stricken passenger.
"Our thoughts are with our customer at this time," the statement read.
Just prior to arrival, a pilot told the control tower that passengers who were nurses were attending to another "unresponsive" passenger."
"So they're working on her right now," the pilot said in a public recording of the conversation on liveatc.net.
Twitter messages posted by other passengers aboard the plane reported that Fisher had fallen ill, with one saying she had stopped breathing.
"Don't know how else to process this but Carrie Fisher stopped breathing on the flight home. Hope she's gonna be OK," wrote filmmaker and YouTuber Anna Akana.
Comedian Brad Gage wrote, "I'm in complete shock. Anna Akana and I sat in front of Carrie Fisher on our flight from London and she was just taken off the plane by EMTs".
Star Wars co-star Mark Hammill was among those to post their wishes.
Game of Thrones star Gwendoline Christie, who played Captain Phasma in The Force Awakens, wrote: "The whole world is sending you so much love! Sending you the universe's most powerful Force."
Warwick Davis, the Ewok Wicket from Return of the Jedi, tweeted a picture of himself with Fisher.
Fisher is the daughter of famous Hollywood couple Debbie Reynolds and Eddie Fisher.
Fisher is considered Hollywood royalty who has written and spoken openly about her struggles in Hollywood. She took on her prickly relationship with her mother in the book-to-movie Postcards From the Edge. She's also been outspoken about her mental-health issues and the solution she's found – radical-sounding electroshock therapy.
She made her big-screen debut as a teenager in the 1975 comedy Shampoo. Her big break came in 1977 as the intrepid Princess Leia, her hair twisted into braided side buns, in the first of the Star Wars movies.
Fisher made headlines in November with the disclosure that she had a three-month love affair with her Star Wars co-star, actor Harrison Ford, who played the swashbuckling pilot Han Solo, during the making of the original film in 1976.
She reprised her Princess Leia role in two sequels and returned last year in Disney's reboot of the franchise, The Force Awakens, appearing as the more matronly General Leia Organa, leader of the Resistance movement fighting the evil First Order.
Los Angeles Times, AP, AAP