Airport operator BAA has mounted another legal challenge to try to avoid having to sell Stansted Airport.
The Competition Commission (CC) ruled as far back as 2009 that BAA must sell Stansted in Essex and two of its other UK airports.
BAA has mounted a series of legal challenges to the decision - all of which have ended in defeat for the Spanish-owned company.
BAA said it had started appeal proceedings, saying it believed the ruling over Stansted was "flawed".
Since the CC decision, BAA has sold Gatwick Airport in West Sussex and, faced with having to dispose of either Edinburgh Airport or Glasgow Airport, has opted to sell Edinburgh.