Carrie Fisher suffered a massive heart attack Friday on an airplane … TMZ has learned.

Our sources say Carrie was on a flight from London to LAX when she went into cardiac arrest. People on board were administering CPR.

The plane landed just after noon in L.A. and paramedics rushed her to a nearby hospital.

Fisher, who became famous, of course, as Princess Leia from “Star Wars,” has been on a book tour.

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