THE LATEST REPORTS from the Federal Aviation Administration suggest that if all goes well the DC10s will be back in the air this week. The safety investigators believe they have found all the defects that are possible to find, and they are now discussing technical details about how and when the planes should be modified and inspected. Their judgment appears to have convinced the FAA that the planes are airworthy. Whether it will be sufficient to convince a federal judge, who ordered the DC10s grounded about the same time the FAA did, is something else.

From all outward appearances, the FAA's investigation has been thorough and carefully conducted. The DC10s have been on the ground for five weeks, and both the planes and their repair records have been scrutinized. No other commercial airliner has been subjected to such detailed treatment after an accident. But no airliner has been the subject of so much informed and deserved criticism.

The FAA has found - and it believes corrected - shortcomings in several elements of the plane's systems: Its engine mountings, control cables, hydraulic systems and electrical warning systems. The principal flaw is the faulty engine mounts: The other parts that failed on the Chicago-crashed plane failed only after the engine had broken loose from the wing.

Thus, the key judgment being made by the FAA is that the pylons that hold the engines will not fail without warning and the warning can be spotted in time if the pylons are inspected after every 100 hours of operation. Once the planes are flying again, it will be up to the FAA to make sure the airlines meet that rigorous inspection schedule and that the parts that have to be dismantled to perform it are put back together properly.

Other problems have been discovered. An argument can be made that the FAA should require the relocation inside the wing of the hydraulic system and, perhaps, the installation of another backup system. But changing the location might make the systems vulnerable to a different kind of accident. Apparently, the experts have become convinced that the pilot of that ill-fated plane could have saved it if he had known precisely what was wrong. That is why the focus for modification of the plane's parts has shifted to the installation of an additional electrical system to keep the warning instruments in the cockpit functioning.

Judgments of this kind involved an expertise far beyond the possessed by most of those who fly in these huge airliners. Their safety is in the hands of the FAA and those experts upon whom it relies for guidance. Not only must the FAA be convinced the judgments it is making in this particular case are right; it must also be able to convince the public first of the thorughness of its work and second that it has greatly improved its procedures for maintaining air safety. The latter will require some changes in its relationships with the airlines. It needs to have much more information in its hands about the performance - and problems - of all airlines, as a routine matter, than it hadconcerning the DC10 before the Chicago crash.