Feuding investors in a California plane startup are firing off allegations against each other while the company is in the midst of a U.S. national security review , a risky tactic during the secretive process. Icon Aircraft Inc. makes a small, amphibious plane with foldable wings that is marketed for recreational use. A group of American shareholders fell out with Chinese investors who hold a dominant stake in Icon, alleging they are improperly transferring the company’s technology to China. The Chinese investors have said in legal filings that they are pursuing a normal technology licensing agreement. They and Icon deny…