The collision of two airliners last Friday at Los Angeles International Airport, an accident that claimed 34 lives, is prompting a new look at airport safety practices.

The picture that emerges is not flattering to air safety officials even though commercial aviation remains one of the safest modes of transportation. It shows that air safety officials have been slow to take accidents on the ground as seriously as they should. And it shows that the ability to monitor planes for safety has not kept up with the soaring growth of air travel.

To describe the problem is to suggest what's needed for its solution. Fortunately, some remedies were in the works even before the tragedy at Los Angeles. But much more remains to be done.

The potential for more such tragedies is indicated by the growing number of near-collisions on the ground at American airports with control towers. Such incidents have risen from 179 in 1988 to 267 in 1990, an increase of almost 50 percent.

Air travelers can take some satisfaction from the impending move by the Federal Aviation Administration to make runway and taxiway markings standard throughout the nation, a decision that was made before the collision Friday in Los Angeles between a SkyWest commuter plane awaiting takeoff and a landing USAir Boeing 737. The change makes sense; runway and taxiway markings now vary so much from airport to airport that they can confuse pilots, particularly those using an airport for the first time.

But the fact that the FAA began recording near-collisions on the ground only a few years ago raises questions about what else the agency may be overlooking or slow to deal with.

Preliminary indications that an air traffic controller may have been at fault in the Los Angeles collision also breathe new life into old concerns about the quality and quantity of the nation's controllers.

Those questions have persisted since President Reagan fired 11,400 of the FAA's air traffic controllers after they staged an illegal strike in 1981. As late as 1986, there were 14,080 controllers, compared to a pre-strike level of 16,400. By last fall, the number of controllers had reached 17,266.

But air travel has increased so much that another 3,000 controllers are needed.

Then there's the matter of quality. Before the strike, about 80 percent of the controllers were rated as being at full-performance level, meaning that they were fully trained to perform each of the controller positions in their control tower such as ground, departure, and arrival control. By 1984, the ratio of full-performance controllers had fallen to 72 percent. By last fall, the figure was down to 62 percent. The decline means, among other things, that supervisors have less flexibility in making work assignments.

The collision at Los Angeles should reinforce an old lesson: Aviation accidents are usually so complex that they seldom yield to a simple remedy even when human error is involved. Even human errors often have their roots in mechanical and administrative shortcomings in the aviation system. That system, good as it is, still needs constant refining.