The 60-year old, who has previously battled drug use and bipolar disorder, was on a flight from London to Los Angeles when she fell ill.

She was reported to be in a critical condition, and is still in an intensive care unit, according to her brother .

Airport staff confirmed a passenger was rushed to hospital after suffering a heart attack.

Her Star Wars co-stars Mark Hamill and Peter Mayhew have expressed their concern on social media. (Euronews)

as if 2016 couldn't get any worse... sending all our love to @carrieffisher

— Mark Hamill (@HamillHimself) 23 dicembre 2016

Thoughts and prayers for our friend and everyone's favorite princess right now.. @carrieffisher

— Peter Mayhew (@TheWookieeRoars) 23 dicembre 2016