WASHINGTON — The U.S. air transportation system needs major structural changes to meet an expected doubling of demand within 35 years, the National Research Council said Tuesday.

Cleaner, quieter aircraft are keys to increasing the system’s capacity, the report said. Otherwise, it said, public objections to the noise and pollution caused by airplanes will limit airport growth.

The council recommended a focus on investing in improved aircraft designs and new propulsion technologies such as hydrogen fuel and advanced fuel cells.

"Business as usual, in the form of continued, evolutionary improvements to existing technologies, aircraft, air traffic control systems and operational concepts is unlikely to meet the needs for air transportation that will emerge over the next 25 to 50 years," said the report, which was sponsored by NASA and the Federal Aviation Administration.

Steve van Beek, spokesman for Airports Council International, said the airport advocacy group endorsed the concept.

"We have fought a long and sometimes lonely battle for higher standards to promote quieter aircraft," van Beek said.

Other kinds of aircraft that could contribute to a more efficient air transportation system include supersonic business jets, giant flying wings for carrying cargo, and aircraft that can take off and land vertically without runways, the report said.

The report also noted that the United States lacks an important goal for civil aeronautics that Europe recognizes: satisfaction of consumer needs.

"This could be a major oversight, given the large role that consumer demand for low cost and convenience (e.g., frequent departures) plays in business decisions made by industry," the report said.

Another flaw in the U.S. vision for aviation is that it doesn’t aim to continue its dominance of the aeronautics industry, while Europe is intent on overtaking the United States, the report said.

The report, written by people representing industry, academia and the government, notes that a group named by the European Commission set forth a vision for European aviation in 2020. Among its goals was primacy of the European aeronautics industry, a supersonic aircraft that would carry 1,200 passengers, and an air traffic system that would set the world standard for efficiency.

"They have a strategy and we don’t," said John Hansman, director of the International Center for Air Transportation at the Massachusetts Institute of Technology, who reviewed the research council’s report.

"The Europeans’ intention to be premier in aerospace has been something of concern in U.S. aeronautics for several years," he said.

Hansman said the report was prompted by misgivings about Europe surpassing the U.S. aeronautics industry and the probability that demand will return to 2000 levels, when travelers complained about overcrowded airports and frequent delays.

The FAA’s 266 control towers now handle a daily average of 200,000 landings and takeoffs, including military, passenger and cargo flights.

The report noted that satisfying security requirements will become more difficult in the future. The authors didn’t delve into the problem, though, because they felt other people are taking a hard look at aviation security, said Alan Angleman, the National Research Council’s study director.

The report said problems with the air traffic system should be dealt with by manufacturers, airlines, pilots, passengers and government agencies working together.

The government recently acknowledged the need for a unified approach to aviation policy by establishing a joint office involving the FAA, NASA and the departments of Commerce, Defense and Homeland Security.

The research council is the main arm of the National Academy of Sciences and the National Academy of Engineering, nonprofit institutions that provide advice on science, technology and health policy.

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