THE FEDERAL Aviation Administration has apparently found a "quality-control" problem in the way certain parts of the engine mounts of the DC10s were assembled. The cracked bolts found on about 30 DC10s could have led to serious accidents. The encouraging aspect of this chilling news is that it is unrelated to the cause of the crash in Chicago last month and so many indicate that the FAA is giving the DC10s the thorough study they deserve.

If that study is to reestablish public confidence in the safety of the DC10s, it must go well beyond the immediate causes of the crash in which 273 people died. Too many questions have been raised about other aspects of the plane for the FAA or the National Transportation Safety Board to let it fly again until both groups are prepared to vouch for its airworthiness.

The temptation to abbreviate the investigation is strong. McDonnell Douglas and the airlines are pushing to get the planes back in the air quickly. Their financial losses grow day the planes sit on the ground. And many European safety agencies have already given the planes the green light, indicating their agreement with McDonnell Douglas that the DC10s are fundamentally sound.

But temptation must be resisted. While the FAA does have a legal responsibility to consider the economic well-being of the airlines, its paramount concern must be safety. Until its experts are able to certify that they found all of the discoverable flaws in the DC10s - until they are willing to fly on the planes personally as a routine matter - the DCios should be kept where they now are: on the ground.