Viking SF-2A Cygnet
 The Viking SF-2A Cygnet also called the Sisler SF-2A Cygnet and the HAPI SF-2A Cygnet is an American STOL amateur-built aircraft designed by Bert Sisler and produced by Viking Aircraft. The aircraft is supplied in the form of plans for amateur construction. The Cygnet first flew in 1973.The Cygnet plans were originally marketed by the designer through his company Sisler Aircraft of Bloomington Minnesota and later by HAPI Engines a supplier of Volkswagen air-cooled engines.