Gatwick, Britain's second-largest airport, has been put on the market by its Spanish owner BAA. The airport has been valued at £1.8bn.The decision comes barely a month after the Competition Commission said BAA might have to sell three of its seven UK airports because of market monopoly concerns and poor service for passengers.Interested parties are thought to include Germany's Hochtief, Global Infrastructure Partners, the GE-Credit Suisse Investment fund and Australian company MacQuarie.