Europe's busiest low cost airline, Ryanair, has said that Air Serbia receives large discounts from its hub airport and notes that the airline, together with other flag carriers around Europe which enjoy similar incentives, would be unable to pay them back. The budget carrier's Chief Commercial Officer, David O'Brien, said, "When the regulator demanded for Ryanair to repay all of its discounts at Amsterdam Schiphol Airport, we did so immediately, which once again confirmed our high creditworthiness. But at the same time, no one demanded similar action from airlines such as Air France-KLM. Perhaps because this could undermine their financial situation. What we certainly will soon see, for example, in Serbia, if there is the political will, is a requirement for Air Serbia to repay its debt to Belgrade Airport, which it will be unable to do, in our opinion". Mr O'Brien says that flag carriers enjoy many discounts which are not on offer to Ryanair. Under a takeover agreement between Etihad Airways and the Serbian government, Air Serbia has been exempt from paying a number of services at Belgrade Nikola Tesla Airport. According to the airline's Chairman, these subsidies ended on January 27, 2016.