Photo Credit: NC

For Britney Spears, a December trip to perform in Japan should have been a triumphant moment in her comeback. Instead, it turned into a terrifying ordeal.

"She was in pieces because it was such a long flight," says a Spears family insider.

In order to cope with her crippling fear, the 27-year-old pop star -- who's already on various medications, including antianxiety drugs, to cope with her reported bipolar disorder -- took sleeping pills to help her rest through the flight, the family insider says.

For more on Britney's pill habits, pick up the latest issue of Life & Style, on newsstands now!