A wildcat strike by air traffic controllers in Spain could cost the country's key tourism industry some 400 million euros (532 million dollars), according to a study released Monday. 'The unjustifiable stoppage of Spanish air traffic came on one of the high points for the tourism sector,' with public holidays on both Monday and Wednesday leading many people to take a five-day break, the head of Institute for Economic Studies, Juan Iranzo, told the business daily Expansion. 'The stoppage will mean a high cost that we estimate at around 400 million euros, but it could have much wider consequences for the image of Spain,' he said. 'Overseas, (Spain) now not only has an image of economic crisis but one of institutional crisis.' The IEE produced the study on the tourism impact of the strike for Expansion. Spanish air traffic controllers called in sick en masse on Friday, rapidly shutting down the nation's airspace at the start of one of Spain's busiest holiday weekends in a protest over working hours and benefits and disrupting the travel plans of hundreds of thousands of people. Air services returned to normal on Sunday a day after the government declared a 15-day state of alert which placed the controllers under military command with the threat of jail terms for refusing orders. 'Hopefully, the conflict will have no major long-term consequences, and this will be achieved if air traffic control returns to a normality we have not seen almost all year,' the managing director of Spanish flag carrier Iberia, Rafael Sanchez-Lozano, was quoted as saying in Expansion. Spain was the world's third most popular tourist destination last year after France and the United States, and the sector accounts for around 10 percent of the country's economy. The industry took a battering in the 2008 global downturn and with the emergence of cheaper sunshine destinations in the eastern Mediterranean such as Turkey and Egypt. But it had begun to reemerge this year. The number of foreign visitors rose in October for the sixth straight month despite a drop in tourists from Britain and Germany, its two main markets, government data showed last month. The country welcomed 4.8 million foreign tourists last month, a 4.2 percent increase over the same time last year, bringing total arrivals in the first 10 months of 2010 to 47.2 million, up 1.2 percent, the tourism ministry said. 