FREDERICK, MD. -- From his office overlooking a small airstrip lined with Cessnas and Pipers, John L. Baker holds a newspaper clipping in which the president of American Airlines comments about restricting small-airplane traffic around major airports.

Head of the largest general aviation group in the country, Baker mulls over the appropriate retaliation. Perhaps general aviation pilots should boycott fuel and services from American's 37 flight service stations. Maybe they should boycott American in general.

"Our membership is very mobile and very affluent and, by and large, most people don't use little airplanes to fly long distances," he said.

Baker, scrappy and outspoken in defending the rights of general aviation, decides to suggest these things in a letter. American's airplanes may be larger than Baker's, but they do not always outweigh him in clout. Next to the airlines, the Aircraft Owners and Operators Association (AOPA) is one of the most powerful forces in determining national aviation policy.

Through its lobbying, the group was primarily responsible for delaying legislation -- proposed several years ago and finally passed last year -- that created stricter air traffic controls around the country's busiest airports.

The organization also used its muscle when the Federal Aviation Administration closed off a general aviation flight route around Los Angeles last August. The general aviation pilots raised such a clamor that the FAA announced three months later a new general aviation route would be opened in February.

Now AOPA is leading the drive against the Massachusetts Port Authority plan to raise landing fees and restrict access to Boston's Logan Airport.

"Our major concern about losing this issue at Boston is that there are a number of major metropolitan airport operators around the country who are watching this like a hawk," said Dan Todd, senior vice president of AOPA's government and technical affairs. "It's just going to spread like the plague."

Since Christmas week, when the proposed changes at Boston were made known, 250 letters have been sent to Boston officials, Gov. Michael S. Dukakis (D), the FAA and the Transportation Department.

The general aviation pilots also met for an hour last week with Transportation Secretary James H. Burnley IV. Although the department has no direct influence over Massachusetts port officials, a 60-minute meeting with Burnley is regarded as a measure of the pilot organization's stature in the aviation community.

With more than 260,000 members, the organization finds its strength, in part, from its size. AOPA can quickly deploy personnel, raise money, or bury a member of Congress or an agency in mail. "We can reach more pilots than the government can on short notice," Baker said.

When the restrictions on Los Angeles were announced last August, the general aviation pilots bombarded the FAA and California's congressional delegation with 50,000 letters and postcards, bought full-page newspaper advertisements calling for then-Transportation Secretary Elizabeth Hanford Dole's resignation and raised $500,000 -- from 18,374 contributors -- to finance a suit against the government.

"We have the muscle to back up what we say," Baker said. "We're not go along-get along. Our members send their money to AOPA with a guarantee we'll fight on their behalf."

The fight sometimes puts AOPA at odds with the airlines, and Baker is particularly irritated at American's president, Robert L. Crandall, who manages to work at least one spicy, quotable remark about the need for restrictions on general aviation into almost every speech.

AOPA operates at a 5-year-old headquarters at Frederick -- a modern, glass-and-chrome office building just across the street from an airstrip where staff members practice takeoffs and landings on clear afternoons. The organization has a $24 million annual budget, employs about 200 people and, in addition to lobbying Congress on behalf of general aviation pilots, operates a telephone hotline. It receives about 5,000 calls a month from pilots calling with questions from requests for information about flying conditions in Alaska to queries about blue book prices on a used Beechcraft Sundowner.

The organization runs a mail-order business and supplies charts and maps to pilots, publishes a monthly magazine and provides information about pilot medical certificate requirements, tax issues, airport closings and current fuel prices at 1,300 locations around the country.

The pilot organization also maintains a "VIP List" in its computers, tracking pilot members who are on a first-name basis with senators, House members, governors, state legislators or any other public officials. The list is not used much, but is kept up to date because of its effectiveness in the past.

For instance, when then-Sen. Birch Bayh (D-Ind.) chaired the Senate aviation subcommittee and opposed AOPA on flight service stations, the pilots checked their computer files. "Within one day, we had 115 calls into his office," Baker said. "That's the whole concept. Someone with credibility who is willing to use that with a member to talk about aviation."

Baker, a former Justice Department lawyer, FAA official, military pilot and Air Line Pilots Association executive, is known for his bluntness in defending the interests of general aviation. Over the years, the organization's zeal in protecting the rights of member pilots earned the group the name the NRA of aviation. By coincidence, one of the pilots' lobbyists, Judy Bassett, used to work for the uncompromising National Rifle Association.

"I don't think that's entirely a pejorative term," Baker said. "If that means we're effective, I'll happily wear the title. We're not at all reluctant to use our muscle to participate in the political process.

Despite its lobbying successes, AOPA is battling eroding public support. The August 1986 midair collision of an Aeromexico jetliner and a small private plane that illegally entered restricted airspace over the Los Angeles suburb Cerritos, killing 82, cost AOPA some of its influence in Washington.

"After Cerritos, they began losing clout," said a congressional aide who works for one of the aviation subcommittees. "What had been their basic tenet -- the 'we have a right to fly' -- doesn't get the same kind of hearing up here."

The number of near collisions last year topped 1,000, and most involved at least one small plane.

AOPA recognized the mood change and countered with an educational campaign to inform the public about general aviation. It bought an advertisement in The Wall Street Journal with the Air Line Pilots Association to talk about shortcomings of the air traffic control system.

"We aren't representative of just the Sunday flier," Baker said. In fact, the association's statisticians estimate pleasure flying accounts for about 5 percent of the 35 million air hours flown by general aviation pilots annually. The group encompasses air taxis, corporate jets and charter planes.