THAT NEAR-COLLISION last month of an Eastern Air Lines shuttle and a helicopter at National Airport -- coming as it did in the midst of a record number of airline fatalities and other mishap reports -- has brought the whole range of public questions about air safety closer to home but still without clearcut answers. In this particular incident the Federal Aviation Administration placed an air traffic controller on administrative leave after a preliminary investigation indicated she gave permission for the helicopter to take off on a course that would have placed it in the path of the jet. So what does this say about traffic at National -- or air traffic anywhere? Specifically, should helicopters be banned at National as menaces to big-jet travel? And if so, what about those general aviation planes that use National?

Experts caution against reading too much into this one incident -- and it's a good point. But some of these same experts also assert that National's runways are inadequate and that approaches to the airport are difficult. And then there's the air controller system: how good is it at National -- or in general?

Contrary to what many may believe about helicopters getting in the way, they are not ordinarily a problem at National. Normally, helicopters take off in a path out of the main traffic entirely and across no runways. With clearance from the local controller, a helicopter controller (assigned exclusively to helicopter traffic only at peak periods) may grant permission to take off across a runway. Maybe this permission should be refused at all times. But experts see no reason to ban helicopters, which are considered as part of general aviation. General aviation traffic is limited by a slots system for bad weather conditions (in which smaller planes aren't likely to fly anyway).

Quite aside from whatever findings emerge in the case of the near- collision, concern about the increasing frequency of runway incursions has prompted the FAA to ask controllers to increase their vigilance. A congressional report this month concluded that the margin of safety had diminished in air travel because of fatigue and stress on the part of controllers.

Yet in most accidents this year controllers were not found to be a factor. All sorts of different conditions have been cited, from contaminated fuel to overloading and faulty parts. This year's record number of fatalities just may have been an unlucky string of occurrences; statistics still show flying to be a safe way to travel.

Nevertheless, more intense airline inspections, improved warning equipment and a bigger and better trained corps of controllers are needed. Transportation Secretary Elizabeth Dole has taken a number of initiatives, including increasing the number of air carrier inspectors; increasing the number of controllers; completing action on tougher drug- and alcohol-use restrictions on flight crews; establishing tougher flammability requirements for airplane seat cushions; and pressing for higher civil penalties for safety violations.

It will take months to years before these policies have any significant impact. For the same reason, improvements in the physical conditions at National should be started as quickly as possible. There is no need to wait for another scare -- or tragedy -- before acting.