Actress Carrie Fisher suffered a heart attack on a Los Angeles-bound flight Friday, law enforcement officials confirmed to NBC News.
Fisher was in full cardiac arrest on the plane and rushed to a local hospital. She was reported to be in stable condition at Ronald Reagan UCLA Medical Center several hours later.
Her brother, Todd Fisher, told The Associated Press that she was "out of emergency" and stabilized. He said he could not discuss any other details about what happened.
Passengers were administering CPR on the flight heading from London to Los Angeles International Airport, according to TMZ.
A source told NBC that her condition was "not good."
United Airlines released a statement about reports of an "unresponsive" passenger on one of their flights, but did not reference Fisher in its comments.
"Medical personnel met United flight 935 from London to Los Angeles upon arrival today after the crew reported that a passenger was unresponsive. Our thoughts are with our customer at this time, and any requests for additional information should be directed to local authorities," the statement read.
The Los Angeles Fire Department said paramedics "were standing by for the plane's arrival, provided Advanced Life Support and aggressively treated and transported the patient to a local hospital."
A passenger on board the flight told NBC4 the crew made an announcement 20 minutes before the flight landed to ask if there were any nurses or doctors on board.
Fisher is best known for her role as Princess Leia from "Star Wars."
Mark Hamill, Fisher's co-star in the "Star Wars" movies, tweeted that he is "sending all our love" to Fisher.
Actor Peter Mayhew, the man behind the mask of Chewbacca, asked fans in a tweet to pray for "everyone's favorite princess right now."
Thoughts and prayers for our friend and everyone's favorite princess right now.. @carrieffisher
— Peter Mayhew (@TheWookieeRoars) December 23, 2016
Fisher recently finished filming "Star Wars: Episode VIII," which is the second of three new films in the "Star Wars" saga, noted NBC News.
NBC News Investigations' Andrew Blankstein and NBC4's Marin Austin and Jessica Rice contributed to this report.