OLD HABITS DIE hard. The other day James Fletcher, NASA administrator in the 1970's, who has been called back by President Reagan to rehabilitate the damaged space program, made his first major speech since resuming office. Mr. Fletcher has taken over a badly troubled agency. The space shuttle Challenger blew up in January, killing all seven aboard. Since then both the Titan and Delta rockets used for unmanned launches have also failed. Inquiries are now under way in all three cases, and in a sense it can be said that the United States is temporarily without the means, for the first time in years, to put a major object in space.

Nor is it clear that this is all bad luck. Inquiries since the Challenger accident, including by the official commission appointed by the president, have largely done in NASA's old reputation for clean-cut and flawless efficiency. For years, including those during Mr. Fletcher's first term as administrator, the agency has been in a running battle with federal auditors, who have attacked it for being poorly managed. The presidential investigative commission has found that agency officials also knew for years of the problem with O-rings now thought to have brought Challenger down, and the night before the launch these officials beat down engineers from Morton-Thiokol, the booster manufacturer, who said the launch would be unsafe. NASA has also been what you might call less than enthusiastic about helping with the investigation. Commission chairman William Rogers accused it two weeks ago of having "almost covered up" some aspects of the case.

So what has Mr. Fletcher learned? How does he plan to turn his agency around? What does he say in his maiden speech?

Well, essentially he says that NASA's problem is the press. He complains that an unnamed "small segment" of the press has distorted NASA's history and is ruining its image. NASA, he says, "is more than another government agency. As a symbol of American aspiration and achievement, it is a vital national asset.

The press -- those small segments, in any case -- no longer is treating NASA in these reverential terms. For years it did. That is what Mr. Fletcher is used to, and would like to have back. Instead, the press is treating the agency as it does most other parts of government, holding it accountable (as indeed it has a fair amount to be accountable for), harrying it. "If this kind of coverage continues," Mr. Fletcher told his audience of industry executives, "I worry about whether it could do irreparable damage, not only to the agency . . . but also to the nation as a whole." And then he gets to the important part. "For example, could such continued coverage cause public support, and thus, congressional support of the NASA program to diminish to the point where the program itself could be in jeopardy?"

Mr. Fletcher, you've got it wrong. That may be the way it used to be; it's not the way it is. The serious problem you've got on your hands is not a problem of image, but of substance. You alter it by changing the structure, not the paint. You're right that NASA over the years "has done magnificent and creative things." It turns out that in recent years it's done some pretty bush-league things as well. Those are why your press is bad; fix them and the press will be just fine. But don't try to run this glamorous agency by press release any more.