A stewardess caused panic by repeatedly screaming "We're going to crash" when a packed plane hit turbulance.
The Virgin flight hit bad weather three hours into a journey from Gatwick to Las Vegas.
Some passengers were sick and others thrown from their seats as luggage, drinks and trays were tossed around.
Those using the toilet at the time were stuck in the cubicle while others prayed and cried.
And their ordeal was intensified by the screaming stewardess.
Passenger Paul Gibson told The Daily Mirror: "She began screaming every time the plane shook.
"She shouted at the top of her voice, 'We're going to crash! We're going to crash! We're going to crash!"
The un-named woman - in her mid 20s - also lobbed sick bags across the cabin when poorly passengers screamed for more.
Crew members say it was the worst turbulance they had encountered.
A spokesman for Virgin said no complaint had been received.
"Turbulance can be a very frightening ordeal," he added.