Stansted Airport is to be sold to Manchester Airports Group for £1.5billion.
The group is the largest UK-owned airport operator and owns Manchester, East Midlands and Bournemouth airports.
Colin Matthews, chief executive of Heathrow Airport Holdings, formerly BAA , said: "Stansted Airport and its people have been part of our company for a long time.
"It has been named by passengers as ‘the world’s best airport for low-cost airlines’ for two consecutive years at the Skytrax World Airport Awards, and we are proud of its achievements.
"We wish the new owners every success and are confident the airport will continue to flourish.
"We will continue to focus on improving Heathrow, Glasgow, Aberdeen and Southampton airports".
The Competition Commission ruled in 2009 that BAA had to sell Stansted and Gatwick due to concerns over a lack of competition between the three major airports.
Appeals and counter appeals followed until the company decided to put the Essex terminal up for sale last summer.