In an email to customers, low-cost airline Ryanair warned that a possible decision to increase airport fees by Spanish airport operator AENA may lead to increased ticket prices, Spanish daily ABC reports. It has already expressed its disapproval of such a decision on previous occasions. AENA is considering to increase airport fees by 18.9%.Ryanair is the main flight operator in Spain in terms of the number of passengers. It advised customers with upcoming scheduled flights of the possibility that their tickets will see a slight price increase.The company revealed that it intends to pass higher fees to its customers and explained that it may be forced to charge passengers as a result of any airport fee increase imposed by the government ahead of affected flights.IBERIA AND AIR EUROPA ALSO OPPOSE FEE INCREASEThe strategy director at IAG's Iberia, Jose Bolorinos, warned last week that elevated airport fees on top of the two to three per cent annual losses already generated by low ticket prices in the sector would be "disastrous".Bolorinos pointed out yesterday that airport fees are a "key" element in airlines' structural costs. He added that fuel costs, which make up 30% of ticket prices, have been rising while ticket prices have been falling in recent years.Similarly, Air Europa President Juan Jose Hidalgo explicitly described that airlines have had to accept the fees imposed by the government and AENA "whether they like or not." Hidalgo explained that the new prices would impact annual earnings by around €30m.MD