Bill Farrar, 51, of Germantown, says he spent about 17 years studying traditional martial arts in his youth. Now he wants to brush up on some practical defense moves he can use while traveling for business. "I'd gain, if nothing else, peace of mind in travel," says Mr. Farrar, who will be taking one of the self-defense courses at the Alexandria-area school. "The world has gotten to be an unpredictable place." Bill Farrar, 51, of Germantown, says he spent about 17 years studying traditional martial arts in his youth. Now he wants to brush up on some practical defense moves he can use while traveling for business.

Mr. Higgins began the Executive Force course about four years ago at the request of business executives concerned about their safety on trips. Many found themselves in strange cities or in claustrophobic subway settings where their safety could be threatened. "It's not about being a hero or a vigilante," Mr. Higgins says. "It's about staying alive."

He tinkered with the class in the weeks following September 11, adding new material specifically for travelers on airplanes, and watched interest soar. "You don't have to have years of training. You don't have to be in shape," he says of the course.

His students range in age from 30 and 50. "They used to be athletic, but they've let their bodies go," he says. Carol Middleton, director of the D.C. Self-Defense Karate Association, says airline staffers aren't the only ones seeking self-defense training. "The people who aren't airline personnel are dying to get into it, too," Ms. Middleton says.

They learn that fending off an attacker in a confined space such as that found on a plane or a bus poses some problems. "You're in a very limited area, and there are a lot of vulnerable people around," she says.

Cramped quarters add one benefit for those under attack, however: "They can't be coming at you from all directions, like on the street, " she says. People can learn to use their airplane seats, which are easy to pick up because they double as flotation devices, and use them as shields. An airline blanket can be used to cushion a blow from a box cutter or other weapon.

Knowledge of judo, a form of karate, may have played a key role in the heroism of passengers aboard Flight 93, the hijacked plane that crashed in Pennsylvania on September 11 rather than hitting a target.

Passenger Jeremy Glick, a judo champion, was one of several passengers believed to have fought against the hijackers on that flight.

"Knowing how to defend yourself against terrorists can really save lives," says Rob Colasanti, vice president of the National Association of Professional Martial Artists, a business association for martial-arts schools. He says the martial-arts industry has responded to the public's demand for more courses.

"We see more and more of these type programs popping up," he says. "After September 11, we seemed to think self-defense training was the way to go." It didn't happen right away, he adds. "The schools saw a big decrease in enrollment" after September 11, says Mr. Colasanti, whose group in Clearwater, Fla., has more than 2,100 schools as members. "Then a big spike, up really fast." It doesn't matter if a hulking terrorist squares off against an unarmed, petite woman, he says. Self-defense works. "No matter their size, they have sensitive eyes, a sensitive groin, a sensitive big toe," he says of attackers.

One of the lasting changes wrought by September 11 may be the public's recognition of its role in the battle against terrorism. Tokey Hill, a U.S. Olympic karate coach and security and self-defense specialist, helps average people pick up valuable skills to use against attackers. "As consumers, we have to step up and take a leadership role now," says Mr. Hill, who recently held a series of packed workshops on self-defense in Syosset, N.Y., that emphasized air travel safety.

"We use as much as we know about the September 11 tragedy," he says. "Box cutters are very lethal, but they're very easily defended against. " A seat cushion used as a shield can protect a passenger against the sharp but small blades.

Mr. Hill says the terrorist attacks have resulted in more women enrolling in his courses than ever before. The courses originally were designed for business travelers, but now Mr. Hill sees a variety of clients in his classes, run through the New York College of Wholistic Health, Education and Research, where he serves as a professor in the Physical Arts Department.

Nothing can substitute for a lifetime studying the martial arts, but Mr. Colasanti says a short class is much better than nothing. "You can see a lot of progress very quickly," he says. Gloria DuBissette, director of Gentle East Martial Arts, which has locations in the District and Maryland, says September 11 "just made everyone more aware of their vulnerability." "You can't leave security to the police," Ms. DuBissette says. "You have to be alert."