Britain's consumer affairs watchdog said today it was opening an investigation into UK airports.
The Office of Fair Trading (OFT) said it would look to see whether current arrangements worked well for consumers.
It said it had not decided whether a more in-depth investigation by the Competition Commission was warranted.
"Nearly two thirds of UK air passengers begin or end their journey at BAA airports," the OFT said in a statement. "Within the London area this rises to nine out of 10 passengers, and in Scotland over eight out of 10 air passengers fly from a BAA airport."
The announcement comes weeks after the country's biggest airports group, BAA, was bought by Spain's Ferrovial.
The Spanish construction group said last month its bidding consortium was ready for any review of UK airports.
Earlier this month, the consortium won a bid battle to buy BAA, whose seven UK airports include London's Heathrow, Gatwick and Stansted, for about £10.1 billion.
BAA has faced calls for its break-up for years because of its dominance of the UK airports sector, which is set to grow as it plans a new terminal at Heathrow in 2008 and a new runway at Stansted by 2013.