He was flying just above the tree line, moments after spraying herbicide on a patch of coca, when the machine-gun fire hit. Eight bullets, probably fired by leftist rebels or drug traffickers, struck the fuselage and tail, knocking out the radio as the cockpit filled with smoke. 

But the pilot, an American under contract in an anti-drug plan that has brought dozens of private citizens into Colombia's drug war, said he knew such attacks went with the job. "Suddenly, you start managing the airplane like you have in the past and have trained for," said the pilot, a 44-year-old Southerner named Mark. "The armor really kept the bullets away from me. There were armor plates under my seat that were damaged. That's where wire bundles were cut that caused the electronics to fail."

In the first interviews among Americans working under a State Department contract in Colombia, a group of pilots spoke today of their experiences spraying fields of coca and heroin poppies that are often guarded by leftist rebels. The Americans, three pilots and a supervisor, agreed to be interviewed on the condition that their full names not be published, for fear of retaliation by traffickers or rebels. 

The pilots, who have spent years flying commercial crop-dusters in the United States, played down the risks here. They view the danger as minimal, they said, because their missions here are well-planned operations using high-tech aircraft, advanced electronics systems and armed escorts, in case their planes are shot down or malfunction. 

"There's always the possibility that something can go wrong at any minute," said Thomas, 50, a Texan who flies search-and-rescue helicopters that aid pilots who encounter trouble. "The guys out there, they're trained professionals, and that's what they get paid to do -- to be there should something go wrong." 

The comments, made during a casual roundtable with two American reporters in Bogota, the capital, came after harsh criticism among some lawmakers on Capitol Hill who feel the United States-financed antidrug program is too heavily reliant on private contractors, particularly pilots who fly spray planes and the helicopters serving as escorts. The four Americans work for Dyncorp, a Reston, Va., military contractor that is operating here under a five-year, $170 million contract. Dyncorp employs 335 civilians here, about half of them Americans. 

Under the $1.3 billion anti-drug aid package that the United States approved last year to cut into Colombia's huge drug crop, no more than 300 American contractors can work here. As of late July, 194 American civilians were working in Colombia, as pilots, mechanics, radar operators, trainers and logistics experts. 

The limit is likely to be reached by December, as helicopters and spray aircraft continue arriving, Ambassador Anne Patterson told reporters in July. The Americans will be needed to fly the planes and to serve as instructors for Colombian helicopter pilots, and as mechanics. 

Some on Capitol Hill are considering whether to allow the number of contractors to increase beyond 300, as the Bush administration has requested. The House has so far placed strict limits on what the White House can do. 

"The administration obviously wants to have maximum flexibility to implement their policy, and Congress clearly wants the administration policy in check," said Michael Shifter, a Colombia expert at the Inter-American Dialogue, a Washington think tank. 

The prospect that the number of private contracters could rise has alarmed some American officials. Representative Jan Schakowsky, an Illinois Democrat, has proposed banning the practice of contracting private citizens for dangerous jobs in Colombia, saying secrecy makes it difficult to hold people accountable. 

"You look at some of the individuals who are involved, you find that they have been involved in covert activities for years," said Ms. Schakowsky. "I'm not comfortable with the lack of transparency, whether it is with the company or with the individuals with those companies." 

Criticism of the contractors prompted American officials to permit the four Americans to talk about their backgrounds, their reason for flying in Colombia and the dangers they face. 

The Americans said the chance at year-round work with benefits -- as opposed to seasonal flying in the United States -- prompted them to look into help-wanted advertisements in trade journals that sought pilots for Colombia. 

Indeed, Bob, 47, a Texan who is married and has three children, said the chance to come to Colombia has given him career stability. In the United States, aerial application, as the pilots call their job, often means weeks of constant travel in search of work, he explained. 

Working in Colombia, he said, is "guaranteed employment for as long as you're here, and it's not commission work." Bob, who has been here six years, said the pilots are paid "flat salaries and benefits, so there is that element of security that we don't typically have as contractors in the U.S." 

The Dyncorp pilots are also well paid, earning at least $75,000 a year; some make over $90,000, and are able to rotate out of Colombia for weeks at a time to be with their families. In the United States, in contrast, spray pilots earn as little as $40,000 (though some earn much more). 

The Americans said they were angered by a report in Semana, a respected weekly here, that quoted an unnamed Colombian police official as saying "the majority of them are high consumers of drugs" and "inject themselves before flying." The report painted them as mercenaries and called them "godless Rambos." 

"We associate mercenaries with something out of the Congo in the early 1960's," said Keith, 44, the supervisor. "We find the mercenary comment quite out of context." 

He explained that the pilots are subject to random drug tests and must pass stringent physical and psychological tests to work in the program. For them, working here under contract is not much different than working under contract to spray insecticides in American national parks or laying seeds over Texas fields. 

The pilots went to great pains to play down the danger inherent in a job that requires long flights into sparsely populated regions controlled by rebels. 

Bob noted that he had been shot at once while flying in the United States, by an irate farmer who was awakened by the sound of the plane. Mark said his wife understood because "she knew I enjoyed flying." The pilots also noted that they do not have search-and-rescue teams accompanying them in the United States. 

Of course, in the United States there is no need for search-and-rescue teams because rebels with AK-47 assault rifles are not shooting at them. Indeed two pilots have been shot down here in recent years, both Colombians; one died. And three Americans have been killed when they crashed, once in 1997 and two the following year. 

For the pilots, the deaths are sobering. But they say they try not to think of the danger. 

"For me the adventure has long wore off," said Mark, who is married and has a child. "It is a back-and-forth business, as we call it. It really just becomes like it is at home: you're out there applying a chemical to a crop. You're concentrating on doing the work that you know how to do."