The National Transportation Safety Board says the pilot's use of performance-impairing medications contributed to a plane crash that killed him and his two passengers in 2010.
The twin-engine Cessna 421 crashed at 10:05 p.m. on July 10, 2010 just north of Tulsa International Airport in Mohawk Park.
The NTSB says Bales owned and was flying the plane. He was Chief Operating Officer of US Highland, while Malmberg was President and Riddoch was Chief Financial Officer.
According to the NTSB, the plane ran out of gas and the medications in Bales' system likely prevented him from getting the plane down safely.
The NTSB says Bales had Cyclobenzaprine in his blood and urine. The drug is a muscle relaxant that carries this warning: "may impair mental and/or physical ability required for the performance of potentially hazardous tasks," according to the report.
Bales also had Phentermine in his urine. The drug aids weight loss and is a stimulant chemically similar to amphetamine.
The report also says Bales had Benadryl in his blood and urine.
The crash illustrates a problem the NTSB has with the way the Federal Aviation Administration licenses private pilots. The problem was the subject of a 6 Investigates story in July.
The FAA does not require private pilots to take drug or blood tests. It relies on the honor system. Pilots are supposed to report the medications they take to the physician who gives them their yearly flight physical, and they're supposed to avoid flying if they take a medication that could affect their ability to fly safely.
Investigators say the three men in this flight left Jones Riverside airport at 9:19 that morning and flew a 3.5-hour flight to Pontiac, Michigan for a business meeting. They say the airplane used about 156 gallons of the 196 gallons of usable fuel in its tanks.
After landing, the airplane was topped off with 156 gallons of fuel for the return flight, but the right main fuel tank sump stuck open, allowing several gallons of fuel to run out. The lost fuel was not replaced before the plane departed for Tulsa, according to the NTSB.
Investigators used data from the plane's GPS unit to chart the flight back to Tulsa. They say the return flight lasted 30 minutes longer than the previous flight.
They say the pilot had been cleared to land on runway 18R at Tulsa International Airport but had not reported any previous problems when he radioed ground controllers, "We exhausted fuel." The plane crashed moments later.
The NTSB says if the pilot had declared an emergency as soon as the plane ran out of gas, he likely would have made it to runway 18L, which was one mile closer to him than runway 18R.
The report says the pilot likely didn't recognize how low his fuel was because of "impairment by the medications he was taking."