Soviet military and civilian airplanes intrude on U.S. airspace about 100 times each year, but the incidents--usually deliberate, according to government officials--always have been resolved peacefully.

The most common approaches are by Soviet military reconnaissance planes, which regularly fly just outside the Air Force's Aerospace Defense Identification Zone (ADIZ), a buffer area 60 to 200 miles wide that surrounds the country. About 70 times each year, the big Tupolev "Bear" jets veer inside the ADIZ line.

"We call it fence-checking," an Air Force spokesman said yesterday. "They probably just want to see what will happen."

What will happen is that U.S. or Canadian fighters intercept the Soviet plane, usually within minutes, the spokesman said. In each case, the Soviet pilot has responded by turning back into international airspace.

In addition, the Federal Aviation Administration says, about 20 times a year a Soviet Aeroflot passenger jet on the Moscow-Havana route flies in U.S. airspace near Florida. Those incidents seem to be inadvertent, according to Jack Barker of the FAA's Atlanta office, and are usually handled with a radio message asking the pilot to go back to his approved course.

No Soviet plane has been authorized to fly in American airspace since January, 1982, when President Reagan suspended most Aeroflot service to this country in retaliation for the Soviet-directed crackdown in Poland. The only exceptions, FAA officials said, are about a dozen Aeroflot flights each year to bring supplies for Soviet diplomatic offices here.

According to the State Department, the most serious Soviet intrusions in recent years involved two Aeroflot flights that left their normal course to fly over a Strategic Air Command base and a submarine base in New England. There was no immediate response in those cases because the Soviets, thanks to a bureaucratic foul-up, had received U.S. permission in advance.

Those curious incidents occurred Nov. 8, 1981, when the FAA was using some inexperienced air traffic controllers after thousands of striking union controllers had been fired.

Aeroflot then had Moscow-Washington service. The airline filed a flight plan calling for its planes to leave their usual course over the Atlantic and pass over a section of New England that included the Trident submarine base at New London, Conn., and Pease Air Force Base in New Hampshire. The FAA, in an action later labeled "administrative failure," approved the flight plan.

The State Department subsequently blasted Aeroflot for "intentional deviations from the operations specifications" and suspended the airline's Moscow-Washington flights for a week.

Another mix-up occurred Oct. 5, 1969, when a defecting Cuban air force pilot flew his Soviet-built MiG to Homestead Air Force Base near Miami. The Cuban pilot evaded U.S. radar, apparently by flying only a few feet above the sea.

At a subsequent congressional hearing, Air Force officials said controllers at Homestead thought the MiG was an American F84 and routinely authorized it to land--on a runway not far from Air Force One, which was waiting to transport President Nixon back to Washington.

Other than those aberrations, however, the Air Force said yesterday that it polices unauthorized air intrusions by constant surveillance and occasional fighter sorties.

The ADIZ is clearly shown on international air charts, the officials said. Any pilot whose plane is to enter the zone is expected to file a flight plan telling when and where this will occur.

A plane that enters the zone without filing this plan is branded an "unknown."

If radio contact cannot be established in 120 seconds, Air Force or Navy fighters scramble to intercept the plane and direct it back to its proper course.

This happens about 1,750 times per year, and usually involves wayward airliners or private planes. The Soviet Tupolevs are the only military planes that regularly make unauthorized intrusions, officials said.

In recent years the air defense system has also intercepted scores of drug-running planes, usually near Miami.

With signals and maneuvers, they are ordered to land. None has been shot at, an Air Force spokesman said.