The Information Commissioner's Office (ICO) is to make inquiries into allegations a Virgin Atlantic employee passed on celebrities' flight details to a paparazzi agency.
Princess Beatrice and Madonna's children are reportedly among almost 70 famous figures whose flight information appears to have been handed to London-based Big Pictures.
The accused employee, a relatively junior member of staff at the airline, resigned in the wake of the accusation but is understood to deny the claims.
An ICO spokeswoman said: "The ICO takes all breaches of the Data Protection Act seriously. Any organisation processing personal information in the UK must ensure they comply with the law.
"We will need to make further inquiries to establish the precise nature of the alleged incident before deciding what action, if any, needs to be taken by this office."
Virgin Atlantic is looking into the allegations and has said it would "deeply regret" any concern caused to the passengers believed to be involved.
Other celebrities whose flight details may have been passed to Big Pictures include Chelsea footballer Ashley Cole; his former wife and singer Cheryl Cole; Tottenham footballer Jermain Defoe; actresses Sienna Miller, Scarlett Johansson and Gwyneth Paltrow; and singers Robbie Williams and Nicole Scherzinger.
A Virgin Atlantic spokeswoman said after the claims emerged: "The allegations that have been raised are extremely serious and we have launched an immediate investigation. The security of customer information is our highest priority and we have robust processes in place to ensure that passenger information is protected.
"The incident that has been alleged concerns eight customers' flights booked in 2010 and we are in contact with all of those people. It is too early to draw conclusions on this matter but of course we would deeply regret any concern that these allegations may cause the individuals involved."
A source at the airline Sir Richard Branson launched in 1984 said it was scanning through email archives and investigating who could access its booking system.