A helicopter flight training school run by a prominent Republican fund-raiser in Nevada has declared bankruptcy, leaving students in 18 states responsible for hundreds of thousands of dollars in uninsured student loans. Now lawyers for several students say they plan to file lawsuits accusing the executive of operating the flight school, Silver State Helicopters, as a pyramid scheme that led to the company's closing. The closing also forced the layoffs of 750 employees at 33 locations, and the bankruptcy declaration halted a binding-arbitration proceeding meant to settle the complaints of 40 students who filed an earlier lawsuit accusing the company of fraudulent business practices. Those students, along with dozens of others across the nation, are working with lawyers in an effort to pursue refunds of at least some of the tuition of about $70,000 that Silver State charged each student.