Still-secret tape recordings made by Japanese electronic listening posts of communications between a Soviet fighter pilot and his military ground controllers suggest to some American analysts that the pilot may have mis-identified the South Korean airliner that U.S. officials say he shot down from behind with a heat-seeking missile.

Two informed U.S. government sources said yesterday that throughout the crucial part of the communications that the Japanese were able to monitor--which covers about a half hour of the 2 1/2 hours that the Soviets were tracking the Korean Air Lines plane--the Soviet fighter pilot never referred to the plane as an airliner but only as "the target."

Speculation among U.S. officials is that Soviet pilots, in the early morning darkness near the Soviet island of Sakhalin, may have thought the big Boeing 747 airliner was an RC135 U.S. Air Force reconnaissance plane, a military version of the smaller and older 707 airliner.

One senior U.S. official said that, based on the available information, the Soviets are guilty of either "enormous callousness" in shooting down a plane they knew to be an airliner yet talked of only as a "target," or "incredible incompetence" in failing to identify properly a 747 jumbo jet of unique size and shape and marked with Korean Air Lines lettering.

Secretary of State George P. Shultz, who yesterday accused the Soviet Union of a "brazen and elaborate" attempt to cover up "the truth that they shot down an unarmed civilian airliner," said earlier that "a Soviet pilot reported visual contact with the aircraft."

Shultz and White House spokesman Larry Speakes branded as untrue new Soviet claims that Soviet fighters had tried to warn the airliner's pilot that he was flying in Soviet airspace and that he had done so intentionally as part of an intelligence-gathering operation.

Sources said yesterday that top U.S. officials anticipated that the Soviets would claim the airliner was on a spy mission and that President Reagan's national security affairs adviser, William P. Clark, asked the deputy director of the CIA, John N. McMahon, to check whether there were any grounds for such a charge. The CIA assured the White House that there were none, the sources said.

One senior official, confirming that analysts thought there was a possibility that the Soviets had mis-identified the South Korean airliner, cautioned that the U.S. intelligence community, working from the translated Japanese tapes, does not have transcripts of the Soviet air-to-ground communications for the entire time that the passenger plane strayed over Soviet territory.

Nor are recordings available of communications with all eight of the Soviet jets that Shultz said were sent into the air to intercept the airliner at one time or another during that period.

He said it was possible that the pilot had told his commanders on the ground at some other point that the intruder was an airliner. But at this time, the source said, indications are that the plane was not identified properly by the fighter pilot.

Another senior administration official said that the statement yesterday by the Soviet news agency Tass made clear that Moscow's "propaganda line for trying to wiggle out of this despicable act" of shooting down a South Korean jetliner with 269 persons aboard is to try to portray the plane as on a spy mission.

Speakes described such claims as "without foundation" as far as the United States was concerned. He added that the South Koreans "were not using that aircraft for any intelligence-gathering" of their own.

U.S. officials said there are clearly much better ways, such as with satellites and radar, to gather intelligence data than to send a passenger airliner of another country on a suicidal mission.

The Soviet statement yesterday and the response by Shultz and Speakes highlighted many unanswered questions about an episode that has shocked and outraged people around the world.

The Tass statement claimed that the Korean Air Lines plane, which the Soviets say flew 310 miles into Soviet airspace and which U.S. officials acknowledge was inexplicably "hundreds" of miles off course, was flying without navigation lights and did not react to "generally accepted" warning signals from the Soviet fighters.

U.S. officials said the transcripts of air-to-ground communications show the Soviet pilots reporting to their ground commanders that the jetliner was "blinking" its lights.

There is dispute over whether the Soviets attempted to warn the plane that it was off course and to force it to land at a Soviet airfield. Yesterday, for the first time, the Soviets said they had fired warning shots and tracer bullets along the airliner's flight path as a warning. They also suggested, by the phrase "generally accepted signals," that Soviet fighters moved in front of the passenger jet and motioned with their wings that the 747 should follow the fighters to an airfield.

Shultz has said that there was "no evidence" that the Soviets had attempted to warn the plane, which, U.S. officials said yesterday, was eventually shot down from behind with a heat-seeking missile.

Shultz also said yesterday that there was also "no indication that the Soviets tried to warn the plane by firing tracers." The communications recorded by Japanese civilian air controllers between the airliner pilot and ground control, which continued to within a few minutes of when the plane was shot down, also give no indication that the pilot saw any tracer bullets or machine gun fire.

Informed U.S. sources said yesterday, however, that there are some "obscure" portions of the tapes from which a deduction can be made that a Soviet fighter may have circled in front of the Korean plane and may have wiggled his wings in a "follow-me" signal.

These sources said, however, that it is not clear how close the Soviet fighter came to the airliner or whether it was a signal. One source said the South Korean pilot probably never realized how far off course he was and, if he saw the fighters, may have thought they were Japanese rather than Soviet.

As for radio contacts, U.S. sources said that Soviet military planes do not carry radios equipped with international frequencies because of fear that their pilots would use them to defect.

The Tass statement, as viewed by Reagan administration officials, also sought to take advantage of some confusing aspects of the incident that may never be cleared up because everyone aboard the airliner apparently was killed, its flight recorder may never be recovered and many details of both U.S. and Soviet actions are secret.

For example, the Soviets questioned why the U.S. government, which appeared from its revelations of details of the incident to be following the progress of the flight, did not contact Soviet authorities to say the plane was off course. There was "ample time," Tass said, during the 2 1/2 hours that the plane was in and out of Soviet airspace.

U.S. officials said, however, that the United States did not track the aircraft all of the time, and Shultz said yesterday that it was "not aware that the Korean airliner was in jeopardy until after it was shot down."

U.S. officials also said the United States was not in the habit of routinely cautioning other country's airliners if they strayed into someone else's airspace and that there was not the slightest thought that a fully loaded airliner would be shot down.

Other aspects of the timing of the entire incident remain puzzling. For example, according to official U.S. accounts, about 12 hours elapsed between when the plane apparently was shot down and when the government first became alarmed that it might be other than merely missing.

Unexplained is why it took so long for intelligence specialists, who listen to air communications as they take place, as well as recording the communications for later study, to get that information to the White House.

One official said that part of the delay can be explained by the fact that the key information was recorded by the Japanese and had to be translated from Russian to Japanese and then to English. But another source suggested that the information arrived in Washington sooner than has been publicly acknowledged.

Another key question is whether Soviet ground commanders actually gave the pilot an order to fire. There are no doubts among those close to the situation that the Soviet fighter pilots were under strict control of their ground commanders.

But State Department spokesman John Hughes acknowledged yesterday that "the honest answer is no" when he was asked if such an order appears in the transcript of communications between Soviet fighters and the ground.

One source suggested that this could be because the recordings were made mostly of the air-to-ground communications and that picking up the communications from the ground station to the fighters is more difficult. U.S. officials, however, have stated flatly that there is absolutely no doubt, because the recordings make it clear, that the Soviet fighter pilot broadcast to the ground that he had fired a missile and destroyed "the target," as Shultz has said.

This raises the question of who authorized the shooting down of the plane. Informed U.S. sources said that intelligence information suggested that the authorization could be traced at least to fairly high military officers, probably a senior colonel or one-star general, according to one source.

Although administration sources said Thursday that the communications reached to Moscow, sources said yesterday that they did not know if the communications went higher in the military chain of command or to civilians.

Many officials said that the Soviets, who have a history of intense military secrecy and sensitivity about the security of their borders, were humiliated by the 1978 episode in which another South Korean airliner went off course and flew 1,000 miles or so into Soviet airspace before being detected, then warned to land and finally shot at and forced down when it ignored the warnings.

American specialists said yesterday that this undoubtedly caused a tightening of the Soviet Air Defense Command and perhaps some clearer orders about authority to fire.

But it still leaves open, officials said, a basic and troubling question about control over Soviet military forces.

Former secretary of state Henry A. Kissinger said yesterday, "If it's a purely military decision, it shows that their command and control system is out of whack. If it's a political decision, then it indicates that they're trying to make a point of ruthlessness."

House Foreign Affairs Committee Chairman Clement J. Zablocki (D-Wis.) said he hoped the "finger on the Soviet nuclear trigger" was not as "unstable as the individual who gave the order" to shoot down the South Korean airliner.