AS THE INVESTIGATION proceeds into that terrible crash at O'Hare airport last week, the picture of the DC10 that emerges is something less than comforting. The plane has a troubling history - more so than any commercial airliner since the Electra - and air travelers are - understandably - unhappy. You could hear talk around town yesterday about ways to keep from flying it.

The Federal Aviation Administration insists that, as far as it knows, the DC10 is airworthy. The derogatory evidence that has been produced in the past week, the FAA says, related to faulty maintenance and inspection requirements and not to defects in the plane's original design. Such defects, if they exist, may not become evident for months until the National Transportation Safety Board concludes its investigation.

Yet, an engine did fall off a DC10 in Chicago. Subsequent inspections revealed that another DC10 was close to dropping an engine and that 67 others had various safety defects in their engine mounts. Five years ago, a cargo door fell off another DC10 and substantial changes had to be made in the interior structure of all the others. Last year, still another DC10 burned at the end of a runway after two tires blew out and its wheels broke. Hovering over all this is the allegation that the plane was put into production much too rapidly in the early 1970s by means of engineering and design shortcuts.

What is an air traveler supposed to think?

The answer of the Airline Passengers Association is that the DC10s ought to be grounded. But the next question is what to do about them once they are on the ground. Since no one has any idea of what, if anything, precisely is wrong with them beyond the engine-mount problems that are being corrected, no one has suggested what modifications could be made to get them back in the air.

This creates a dilemma for the FAA. If it permits the DC10s to keep flying, as it now plans to do, there may be serious accidents. If it should decide to ground the planes and the safety board finds nothing wrong with them beyond the engine mounts, the FAA will be charged with having confounded the air-traffic system deprived the airlines of millions of dollars in revenue, and harmed unnecessarily the reputation of the McDonnell-Douglas Corp., which makes the DC10s.

Put in those terms, the question of grounding the planes appears close. But it can be put differently. Air travelers can get along without the DC10s perhaps better than they got along without United Airlines during its recent strike. Matters of money and an agency's reputation are strictly secondary where life and safety are concerned.

The FAA ought to take another look at the situation - right now. And if there are any doubts at all about the ability of the DC10s to fly safely, they should be grounded immediately.