Carrie Fisher, who played Princess Leia in the Star Wars films, reportedly suffered a massive heart attack, and was said to be in stable condtition.
Reports said it happened on a flight from London to Los Angeles.
The TMZ website reported someone on the plane administered life-saving measures and when the plane landed, she was rushed to hospital.
Her brother is reported to have said the actress is quote "out of emergency", but apparently added little else.
Carrie Fisher, who's 60, is the daughter of Hollywood stars Debbie Reynolds and the late Eddie Fisher.
Fisher has been on a book tour promoting her latest memoir ''The Princess Diarist''.