The Competition Commission has ordered a breakup of ownership of airports in Britain.
BAA has been ordered to sell Gatwick and Stansted and either Edinburgh or Glasgow airport within two years.
During a two year inquiry, the commission looked into BAA's dominance over airports in Scotland and south-east of England.
Commissioner Christopher Clarke says the sale is intended to boost competition between airport, and make life easier for travellers.
BAA currently owns seven UK airports. It has two months to respond to the findings.
The three airports have to be sold in sequence, starting with Gatwick, followed by Stansted, and then finally either Edinburgh or Glasgow to ensure an orderly sale process.
The BBC reports the sale of Gatwick is already underway and possible buyers are being vetted.
BAA was acquired by Spanish firm Ferrovial in 2006 for 10 billion pounds.