AMERICAN AIRCRAFT BUYS INTO HELICOPTER BUILDER <American Aircraft Corp> said it has acquired a 51 pct interest in privately-owned <Hunter Helicopter of Nevada Inc> for an undisclosed amount of stock. An American Aircraft official said the company has an option to acquire the remaining 49 pct. Hunter Helicopter is in the business of building a two passenger helicopter retailing for about 50,000 dlrs each which is certified by the Federal Aviation Administration. The helicopters will be manufactured in American Aircraft's Uvalde, Texas, plant, it added.