Shape Of You Ed Sheeran
Airport operator BAA must sell Stansted and another of its UK airports.
Competition chiefs have made a final ruling.
BAA, which runs six UK airports including Heathrow, will have to sell Stansted first then either Edinburgh or Glasgow airport.
The sale process will start in three months.
The ruling ends a two-year saga which began in March 2009 when the Competition Commission made what was seen then as a final report on BAA's airport ownership.
It is claimed that passengers and airlines will benefit from greater competition with the airports under separate ownership, despite the current Government's decision to rule out new runways at any of the London airports.
The Competition Commission said Stansted should be sold first as it served the larger number of passengers and there would be a small overlap between the Stansted sale and that of one of the Scottish airports.
BAA chief executive Colin Matthews said: ''We are dismayed that the Competition Commission's final decision still requires us to sell Stansted and either Glasgow or Edinburgh airport. The Competition Commission has not recognised that the world and BAA have changed.
''This decision would damage our company which is investing strongly in UK jobs and growth. We have a responsibility to protect our shareholders' investment and we will now consider a judicial review.''
Michael O'Leary, chief executive of budget carrier Ryanair, said: ''We regret that BAA continue to use every legal tactic in the book to delay this (sales) process, and have no doubt that they will continue to use their expensive lawyers to frustrate and delay the sale of Stansted.
''It is now time for the Government to intervene in this shambles and force the early sale of Stansted and one of the Scottish airports and allow competition to provide consumers with more choice, lower costs and a better experience between the London airports.''