To Michael Beltrain, a senior at Arlington County's Wakefield High School, it is simply a matter of patriotism: "If it comes down to any crisis and I have to go, I'll go. I'll be the first one down at the recruiting office and I'll go."

For his part, John Fitzgerald, a 15-year-old Wakefield sophomore, considers it an opportunity to get a head start in the scramble for good jobs: "Another title for this is 'Aerospace Education,' and I figure every little thing helps and this is my golden opportunity."

What both Beltrain and Fitzgerald are talking about is their participation in the first Junior Reserve Officers Training Corps program to be offered in Arlington County public schools in at least 25 years. Organized by the Air Force, it also happens to be the only JROTC program currently offered in any Northern Virginia public school system.

First the victim of a waning public interest in things military in the mid-l950s and then the target of derision in the two turbulent, anti-Vietnam, anti-military decades that followed, JROTC is finally making a comeback in Northern Virginia. The program was begun again this school year.

Nowadays, Monday visitors to Arlington's Washington-Lee, Yorktown or Wakefield high schools are likely to encounter not just young men and women in military uniform but also generally positive attitudes and perceptions about the military and what it can offer.

"Gee, they look great, and they're very proud to be in uniform," said Washington-Lee Principal William Sharbaugh of the first crop of 85 cadets in the county corps. "It's certainly different from what we had 10 years ago in terms of attitude . . . . It's quite surprising when you talk to some of the kids. It's, 'Yes, sir,' and, 'No, sir.' You don't usually hear that from students--unless you're at West Point or the Naval Academy."

The year-long elective course offered at the Arlington Career Center compresses two years of academic and military training into one year for two credits toward graduation. It has drawn what Air Force Sgt. Richard I. Fogg, one of the two county program instructors, calls a "a good cross-section of Americana." Among the students, who travel from their home schools to the center, are 61 boys and 24 girls, of all income, racial and ethnic backgrounds.

That diversity of interest is also apparent areawide. The District of Columbia, for instance, has a successful program now in which 1,420 students are enrolled, while Montgomery County has 409 JROTC students and Prince George's County has 2,350.

Nationwide, the Air Force reports JROTC enrollments of 36,700 students in 285 programs, up from 20 programs in 1966. Using last spring's data, the Marines report an enrollment of 7,946, the Navy, 25,409, and the Army, 113,823. In each case, the military branch involved supplies all uniforms, books and teaching equipment and pays all field trips costs. Half of the salaries for the retired officers who teach the courses is paid by the locality. In Arlington's case, its share is about $23,000, Career Center director Tom Smolinski said.

The impetus for reintroducing JROTC in Arlington came from parents and students, said Rosalie Arnold, the center's coordinator for career programs. Arnold said that after she received requests for JROTC she applied to the major military branches in an effort to get one established.

Arlington won approval from all the military branches, but since there were not enough students or facilities to support separate programs this year, the county chose the Air Force program because it drew the most student interest.

Of other Northern Virginia school districts, only in Fairfax County have parents similarly sought a JROTC program, according to intereviews with area school officials. That effort was shelved because of protests, a school official there said.

"Students today are very career-oriented, very much aware of the job market," Arnold said. "They're very aware of the rising costs of college and of the competition to get into certain colleges . . . . So this provides them an opportunity to look at military life to see if they're willing to make that kind of commitment and it gives them an introduction to various fields, such as engineering, to see if they're really interested in them."

The students who elect to take the five-day-a-week course for two periods a day are under no obligation to the military, which is barred by law from using the program as a recruitment tool. But there are benefits that can accrue from successful completion, such as college scholarships and higher rank and pay upon enlistment.

Such no-strings-attached inducements, coupled with an exposure to new job skills and career choices, seem to outweigh any lingering doubts about the military the cadets or some of their "civilian" classmates may have had about JROTC.

"A lot of kids don't remember the Vietnam War," said career center director Smolinski. "You get a student who's 16 and the war's been over almost half his life."

"I was only 8 when Nixon pulled the troops out and most of the students who are high school seniors now don't really remember Vietnam," said Howard Watson, president of the Washington-Lee senior class.

Kristin Hoganson, a senior who is president of the school's student council association, said that "things seem to be turning more conservative and people don't mind building up the military that much."

Though the JROTC cadets acknowledge being ribbed by classmates occasionally about wearing their uniforms every Monday, their sense of practicality, pride and patriotism emerges in remarks about their reasons for joining.

Beltrain, who wants a career in the Marines, cites the taking of American hostages in Iran for the revival in interest in the military. "The Iranian crisis got people turned around," he said. "We can't let foreign forces tamper with the United States."

"People are more positive about the military now because we don't want to be pushed around by the Russians," said Fitzgerald, who is considering an Air Force career followed by work in the aerospace industry. "I think the younger generation would get up off their butts and fight if they have to."

Instruction takes place in a career center classroom in which maps and flags line the walls beside male and female mannequins in full dress Air Force uniforms and dozens of pictures and models of aircraft. The two instructors, Sgt. Fogg and Maj. Claude D. Greathouse, are both retired Air Force officers.

Here they watch films, like the one screened recently that was assembled from footage of an Allied attempt to bomb petroleum facilities in Romania during World War II. Or they meet with Fogg, a 24-year veteran, for lessons in leadership, Air Force customs and courtesy, and drills and marching. Or they meet for academic instruction with Greathouse, a 20-year veteran who also teaches math and engineering at Prince George's Community College.

They are also going to build and launch their own small rocket while they study the history of aviation, aerospace environment, rocketry and spacecraft, principles of flight and weather, propulsion systems for aircraft and navigation, among other subjects.

It is, Greathouse said, nothing less than a "science course."

But he tries to emphasize the personal experience aspects, too. "I try to cover this as often as possible, but as subtly as possible: When people are killed, they don't reappear in the next episode or become a character in another episode, like the guy who was killed in 'Magnum' showing up on 'The Gold Monkey.' They're gone forever. Say goodbye to them. Dead is dead. . . .

"War is terrible," Greathouse said he tells his students. "We exist as a military so there won't be a war. And if there is, then in some way we have failed."