Vestas (VWS.CO), opens new tab, the world's largest maker of wind turbines, reported on Thursday a surprise adjusted operating loss for the first quarter, hit by lower project deliveries, but stuck to its earnings guidance for the year. It reported an operating loss before special items of 68 million euros ($73 million) against a year-earlier profit of 40 million, on a 5% drop in sales. The mean forecast in a poll of analysts compiled by Vestas was for a 25 million euro profit.