"Noise really is one of the major barriers to airport expansion and the expansion of flights," said Edward Greitzer, an MIT professor who helped run the project. "It gets a lot of complaints." The breakthrough could bring a welcome change to aviation, industry experts said.

"People are still willing to pay more for the convenience of a closer-in airport," said Richard Aboulafia, vice president at Teal Group, an aerospace consulting firm in Fairfax, Virginia. "There is an economic value to being able to keep your air transport close in town, which means you've got to be quiet." REDESIGNED BODY, ENGINES Reducing noise in recent years has been a focus of makers of planes, such as Boeing Co. and Airbus, and jet engines, including General Electric Co. United Technologies Corp. and Rolls-Royce Plc.

While their efforts have mainly involved tweaks to existing technologies, the MIT-Cambridge team set out to redesign the plane from the ground up, with a focus on quiet. Instead of the tube-and-wing model common today, the Silent Jet is a flying wing, evoking current "stealth" military aircraft. It lacks the central vertical stabilizer common at the tail of current passenger jets, instead using a pair of stabilizers at the wingtips.

The proposed plane has a 222-foot (68-metre) wingspan and is 144 feet (44 metres) long from nose to tail, comparable in size to a Boeing 767. "You take the fuselage and you squish it, and you spread it out, and it's an all-lifting body," said Zoltan Spakovsky, an associate professor at MIT who worked on the project. The design allows the plane to remain in the air at slower speeds, which would allow it to cruise in for a landing more quietly. The plane does not use wing flaps, which are common on today's passenger jets and create much of the landing noise.

The MIT-Cambridge team also designed what they said could be a quieter and more fuel efficient engine system. Rather than placing the jets in pods suspended under the wings, the silent jet uses three engines built into the middle of the plane, at the rear. They take in air from above the wing, which helps to insulate people on the ground from jet noise at takeoff. Airplane makers may prove more likely to cherry-pick individual technologies developed for the new jet than to adopt the whole redesign for their products, executives said.

"In a project like this, the idea is to really focus on one goal and see what you could do in the extreme," said Billy Glover, director of environmental performance at Boeing Commercial Airplanes in Seattle, one of the industry experts the researchers have used as a sounding board. "But as you go to a real design process, you have a lot of other trade-offs." Reuters