A Maryland college student who smuggled box cutters onto passenger flights to highlight flaws in airport security, prompting one airline to search every plane in its fleet, was sentenced Thursday to two years' probation.

Nathaniel T. Heatwole, 21, apologized to his family and to federal officials in U.S. District Court, saying it was "never my intention to gain personally through my actions or embarrass the [Transportation Security Administration] in any way."

"I realize that I broke the law," Heatwole told U.S. Magistrate Judge Paul W. Grimm, "and the TSA and the FBI were fully justified in their actions."

When he pleaded guilty in April, Heatwole, of Damascus, admitted that he illegally carried prohibited items into a passenger security screening area at Baltimore-Washington International Airport on Sept. 14. The crime is punishable by up to a year in prison, but the two sides agreed that federal sentencing guidelines called for a term of no more than six months behind bars.

In court Thursday, defense attorney Charles Leeper described his client as a sincere and honest young man, an honors student who had come to understand that his "act of civil disobedience" was misguided. His client's actions, Leeper said, were "born of the view that no government agency would take seriously a 20-year-old who merely reported those concerns. Rather, he would have to demonstrate them."

The prosecutor, Assistant U.S. Attorney Harvey E. Eisenberg, described Heatwole's extensive cooperation with investigators and said: "It is probably helpful in some sense -- although we do not recommend the method -- that someone knows there is a deficiency in the system."

Since his arrest, Heatwole has met with representatives of the TSA, the FBI and a congressional subcommittee. In addition, at Eisenberg's request, Heatwole worked with federal officials to produce a videotape -- in which he explains how he smuggled prohibited items past security -- for use in training airport security personnel.

Before he imposed sentence, Grimm told Heatwole: "It is without question that your intent was positive and good." He said Heatwole's parents, though no doubt anguished by their son's arrest, "likely were proud of the courage you displayed for your convictions."

Grimm told Heatwole, a senior at Guilford College in Greensboro, N.C., majoring in physics and political science, that "the way to effect change is to persuade with the force of reason."

In addition to the term of probation, Grimm ordered that Heatwole perform 100 hours of community service. Heatwole will be allowed to fly on commercial airliners with the permission of his probation office.

The incident, which Heatwole described the next day in an e-mail to the TSA as an act of "civil disobedience with the aim of improving public safety for the air traveling public," prompted the agency to order the immediate inspection of the nation's more than 6,500 commercial aircraft. But the TSA quickly rescinded the order after consulting with the FBI.

Prosecutors initially charged Heatwole with taking a dangerous weapon aboard an aircraft, a felony punishable by up to 10 years in prison. As part of the plea agreement, the charge was reduced to entering an airport area in violation of security requirements, a misdemeanor.

On Sept. 14, Heatwole boarded a Southwest Airlines flight at BWI bound for Raleigh-Durham International Airport. According to a court document, he carried onto the plane three disassembled box cutters, three box-cutter razor blades, matches, about eight ounces of liquid bleach and molding clay "made to resemble a possible plastic explosive." He stashed the items in a restroom, along with a note, so that "any maintenance personnel would not, in his opinion, be unduly alarmed," according to the document.

The next day, he sent the e-mail to the TSA, alerting it to "six recent security breaches"; he had smuggled prohibited items onto planes five times previously. Between February and September 2003, he carried similar items on Southwest flights as he shuttled between Montgomery County, where his parents live, and the North Carolina airport near Guilford College.

In the e-mail, Heatwole provided his name and telephone number and asked to be contacted by authorities. The TSA forwarded the e-mail to the FBI on Oct. 17. Agents interviewed Heatwole that evening at his parents' home. He appeared in court three days later, charged with the felony offense.

Heatwole's legal trouble might not be over. Eisenberg said in court that Southwest Airlines intends to seek restitution. Leeper said Southwest has not filed a civil lawsuit; the airline had no immediate comment.

Nathaniel Heatwole, 21, with defense attorney Charles Leeper, leaves the courthouse in Baltimore after being sentenced to two years' probation. "The TSA and the FBI were fully justified in their actions," Heatwole said.