 Jetliners have become the standard in modern aircraft travel. But fueling these jets is one of commercial airlines' biggest expenses, comprising as much as a third of their direct operating costs. And that's bad news for air travelers who have to foot the bill. Is there a better way? Certainly we can't go back to the pre-jet days. Or can we? That's the question NASA asked when it began taking a serious center to look for an old idea that could help. The people at NASA's Lewis Research Center in Cleveland, Ohio, first started reworking the propeller during the oil prices in the early 1970s. The idea was that aircraft powered by new generation propellers would burn 50-60% less fuel than present-day jets. The design that emerged features eight thin, curved, swept-back blades and is called the prop van. Fifty hours of ground tests were performed on the prop van at lower industries in San Diego. The next step was to get it on an aircraft. And that's exactly what's been done at the Lockheed Georgia Company in Marietta. The nine-foot diameter prop van has been mounted on the left wing of a Gulfstream II business jet. 611 sensors, including 100 microphones, have been placed on the blades and other parts of the aircraft to help engineers monitor its performance. The unique blade design is the key to achieving speeds and altitudes comparable to jets on roughly half the fuel. The propeller to save the airline industry billions of dollars in fuel costs, savings they put in turn pass on their customers. The success of the prop van ultimately depends upon public efficiency. Propeller-driven air currents have traditionally been noisy, so two of the greatest concerns in the prop van project are minimizing noise levels on the ground and creating a passenger problem as far as it jets. To date, this doesn't seem to be a problem. Lockheed senior research pilot Frank Head. Most of the time, we really don't even know what's running inside the cockpit. It's that quiet. And we're only 15 feet away from it. If all goes according to plan, prop vans could start occurring on the nuclear landers in the early 1990s. Advanced propeller research. Rewriting an old concept to make air travel more fuel efficient in the future.