Virgin Atlantic said it had launched an investigation over claims a member of staff had tipped off paparazzi about details of flights celebrities had booked with the airline.
The employee is accused of passing details of eight high-profile customers including actress Sienna Miller and England football player Ashley Cole to the London-based photographic agency Big Pictures.
"The allegations that have been raised are extremely serious and we have launched an immediate investigation," a spokeswoman for the airline said.
"The incident that has been alleged concerns eight customers' flights booked in 2010 and we are in contact with all of those people."
The Guardian newspaper reported that the employee, who looked after high-profile customers for the airline, had now resigned.
It said other celebrities affected included actresses Scarlett Johansson and Gwyneth Paltrow, and singer Robbie Williams.
Miller was awarded GB£53,000 (USD$84,000) in damages from Big Pictures in 2008 over claims of paparazzi harassment.