Sanger says he has seen more than his share of illegal "bootleg" charter operations, and one way to easily smoke them out is to ask about their insurance liability. Depending on the value of the plane, Goldberg says look for a range between $5 million and $300 million. "Get a copy of the policy," Sanger says."If they don't have at least a $10 million policy and you're chartering a jet -- run."

The FAA does require charter companies to carry insurance. But it does not require insurance for non-charter private planes.

That makes it very tempting, Sanger says, for private plane owners to rake in fat profits by pretending to be a legal charter operator.

"They need to pass a law that says you have to have insurance on any airplane, just like they do cars," he says.

When contracting with a non-U.S. charter operator, it gets more complicated. Rules and regulations are different in every country, underscoring the importance of grilling the operator about maintenance, documentation and oversight. Appearances can mean a lot. "Sometimes all you need to do is look at a plane to know you don't want to get on it," Sanger said.

Deadly charter accidents increased in the United States last year, according to the FAA, up from six fatal accidents in 2010 to 16 in 2011, when pilots logged more than 3 million hours in flight. Deaths rose from 17 to 41.

Worldwide so far this year, out of more than 17,600 business jets -- which include small private and charter planes -- there have been 12 major accidents and 25 deaths, according to the Flight Safety Foundation.