By Mike Stone WASHINGTON (Reuters) -The U.S. Army has signed a deal to buy $687 million worth of anti-aircraft Stinger missiles to replenish stocks sent to Ukraine, sources said on Friday. The shoulder-fired anti-aircraft Stinger missiles made by Raytheon Technologies were in hot demand in Ukraine, where they have successfully stopped Russian assaults from the air, and in neighboring European countries which fear they may also need to beat back Russian forces. The contract for a total of 1,468 Stingers was awarded Wednesday, according to a document reviewed by Reuters. There was no timeline fo…