President Reagan is enjoying a warm wash of praise in the airliner incident from parts of the political spectrum that usually treat him with fear and not a little loathing. It isn't so much that these customary critics and doubters to his left think he has pulled off a coup. They are grateful he did not do something irreversible in the way of a military act or a decision to pull out of arms control talks, as some of his supporters--and not only they--urged.

But this sort of praise does Reagan no particular credit and does not reflect a very good understanding of the man. Losing his cool was never something one had to worry much that he would do. He has spent a political lifetime accumulating a reputation for toughness, and this spared him any need to make a fresh demonstration of his mettle now. His view of the Soviets was already dark and suspicious enough to let him absorb this latest incident without a hiccup. Nor would it be characteristic of Reagan to take a political step, like calling his negotiators home from Geneva, that would signify he had erred by sending them in the first place.

In fact, in this instance Reagan's instinct played him true. He accepted that the incident showed no new aspect of Kremlin policy and made not a whit of difference in the global balance of power--two things you could not say about the Soviet aggression in Afghanistan, for example.

True, in his second-day statement ("What can be the scope of legitimate mutual discourse with a state whose values permit such atrocities?"), he seemed on the verge of yielding to a contrary and more far-reaching judgment. But he ended up without accepting or imposing on himself any requirement to reassess the whole range of Soviet-American dealings. He said he had already made his assessment; the country made its by electing him.

That second-day statement shows there was a moment when the White House was vulnerable to thinking, in the classic cold war mode, that the Kremlin had provoked a test of American will. Such a reading, if sustained--it was not --would have demolished Reagan's standard claim that his foreign policy and rearmament have earned new respect for America. It would also have dictated a much more severe American response that would have been difficult to sustain, domestically and internationally.

In any event, cooler counsel prevailed, and the second-day rhetoric trailed off, leaving the president free to treat the incident mainly as a mood conditioner. He did not so much have to set policy and do something or even arrange for others to do something--as he must in Central America--as to take a stand and encourage others to react. For Reagan, it has not been a very demanding crisis. It has really not told much about him at all.

This is not to say he won't profit politically. What he gets is some flak from part of the conservative band, whose alarms serve to advertise his restraint and political independence to other quarters, and some enhanced respect or at least a tactical quieting down among the sector least disposed to trust him before the event. There is agreement that the sequence of Moscow's callousness and Reagan's steadiness has at least temporarily strengthened his hand in dealing with Congress on defense issues, especially the MX.

If this is so, a good part of the praise now arriving at Reagan's doorstep may soon wither. For the crisis may have disturbed the existing political balance between tendencies within the administration and between the administration and Congress. It may have removed some of the restraint imposed on Reagan by congressional determination to dole out funds for the MX only in return for presidential give on START negotiating policy.

Reagan sees these pressures as depriving him of the leverage he needs to get the agreement he seeks. Others, including me, see the same pressures as vital in order to induce a poorly advised president to trim his excessively demanding START proposals to dimensions that meet not only American interests but Soviet interests as well.

Columnist Joseph Kraft said the other day he hoped the president, with his freer hand, would do the statesmanlike thing anyway in order to get a good agreement with Moscow. Second the motion. The airliner crisis reminds us of the ugliest traits of the Soviet leadership. But it does not alter the prior mutual requirement to reduce the risks and costs inherent in the possession of nuclear arsenals. Reagan will finally be judged not by his response in the airliner affair but by his contribution to making the United States more secure. START proposals to dimensions that meet not only American interests but Soviet interests as well.

Columnist Joseph Kraft said the other day he hoped the president, with his freer hand, would do the statesmanlike thing anyway in order to get a good agreement with Moscow. Second the motion. The airliner crisis reminds us of the ugliest traits of the Soviet leadership. But it does not alter the prior mutual requirement to reduce the risks and costs inherent in the possession of nuclear arsenals. Reagan will finally be judged not by his response in the airliner affair but by his contribution to making the United States more secure.