John E. Robson left the government yesterday, but someday he may be back. It's happened before.

The former chairman of the Civil Aeronautics Board - former as of yesterday - first came to Washington from a law firm in Chicago in 1966 as a consultant on economic matters at the Bureau of the Budget. He had decided the job wasn't for him when he first was approached about it by his former law school roommate, then presidential special assistant Joseph A. Califano Jr., but later was subjected to the famous Lyndon Johnson charm that seduced so many others into doing things they at first resisted.

You are the man to head this jawboning program, the President told him. After he ran through all the seasons why he didn't think he was - including the fact that he was a Republican and not a Democrat - and they were knocked down by the President, Robson put out the last reason he could think of. He didn't know anything about the government. "Don't you think it's about time you learned?" the President asked him.

Robson came to Washington.

Since that time, he's learned a lot about the government and how it operates: first the executive offices of the White House then the executive departments - initially as general counsel of the newly established Department of Transportation in 1967 and as its under secretary the next year - and most recently the regulatory agencies. His two-year tenure at the CAB came after a six-year hiatus which he spent back in Chicago at the law firm of Sidley and Austin.

"This is what government is all about to me," Robson said in an interview last week. "You come in to do a job, you do it, and then you leave."

Robson believes there are two ways to try to assess one's accomplishments.One is to look at the particular decisions made during one's time in office and the particular things that go started."I think you have to look at government as a process of ending things and starting things," he says. The second is to look at what might have been accomplished "thematically or having to do with structural change . . .

"I think the major issues we've faced has been regulatory reform," Robson says, "and I would like to think that in addition to the board's specific contribution on that - both the analysis of the issue and the recommendation of a particular legislative remedy - that I have stimulated the industry to think about its own problems, stimulated others to think about those problems, and to seek out remedies for them.

"I think that one of the roles that a chairman of a regulatory agency ought to play is to raise problems, offer solutions, and get the people thinking what ought to be done," he says.

He considers his failures to be the things he didn't get to. One would have been a broad re-examination of the policy and structure of the nation's international aviation policy, which would have had to involve all the splintered government groups that have a piece of it, such as the White House, the State Department, and DOT. He also would have liked to make more progress in the area of decisional expedition and management, a lament that seems to be echoed by nearly every departing regulatory chief.

"In terms of particular regrets, I guess I don't really have that many here that I would say, 'Gosh, now I wished I'd done it all differently.' I tried to say what I thought was right and do what I thought was right, and it hasn't always been agreed with by people here or people outside the agency, but I think I made it pretty clear when I came to the job that that was the way I though it ought to be run," he says.

Though his initial speeches were cautious and rejected "change for the sake of change," Robson became increasingly critical of retaining the status quo in airline regulation and worried that the future of the airline industry without a move to a more competitive system would be grim. "Looking backwards, 40 years of regulation hasn't produced an economically strong industry in pretty good circumstances, so I don't know any reason to feel that 40 more years in not-so-good circumstances are gonna' make 'em stronger," he says.

Without change, "My own belief is that in the long run, the industry will gradually become weaker, that there will be continuing and growing incentives for the board to get further and further into the airlines' activities as a means of controlling costs in order to keep fares down," he sadly predicts. "The long denouement of that, I think, is to increase the responsibility that the agency assumes for the carriers, and when things go bad - when economic forces create problems - the likelihood of ending up with 'em in your lap is a heckuva lot greater." Traditional regulation of the railroads and their eventual performance has to be a lesson for the similarly regulated airlines, Robson contends, a position Senate Aviation Chairman Howard W. Cannon (D-Nev.) echoed last week in a strong speech to the Aero Club in which he pledged to work for a change.

"I just feel that it's a very tough act for the regulator, and I think it's a very tough act for the carriers," he suggests. "If you look at what the carriers say about the regulation they get, they are our harshest critics."

Reducing regulation over a transition period to permit - or force - the carriers to operate in a more competitive environment is the only chance to make the airline industry healthier, more efficient and capable of offering consumers the air fares that will increase the size of the flying public, Robson believes. Why do most of them cling to regultion then? "I don't understand that, I truly don't," he says. "I think that airline management that has lived in the regulatory environment for a long period of time has a very difficult time in perceiving that a different kind of environment would be to their advantage." He thinks they would do well in a more competitive environment and would in fact be a force for accelerating the pace of change once they got used to it.

He disagrees with the board's critics who contend that it could do anything it wanted to promote a more competitive air environment within its existing statute. Besides ambiquities and an underlying "notion of protection" of the individual carriers in the statute, which requires the board to look at what impact the proposed action by one carrier will have on others, a "piecemeal" approach to change is not fair to the industry. "If you do not make the direction clear, you really leave to the vagaries of the appointive process and the courts the ebb and flow of regulatory policy," Robson says. "It strikes me that's a very uneven way for people whose lives and fortunes are so enormously dependent upon what the agency does to have to operate."

Even without legislative change, the board over the past year has approved a number of low fare proposals - Texas International Airlines' "Peanuts" fare and American Airlines' "Super-Saver" fare, for instance - and set in motion a number of proceedings which could result in new entrants and lower fares in a number of markets despite opposition from the incumbent carriers. Future decisions could approve a low-cost cross-country proposal by World Airways, a low-cost transatlantic fare plan by Laker Airways, and several proposals to fly in and out of Chicago's Midway Airport at fares half of those for comparable flights at busy O'Hare. Some believe political pressure for lower fares may assure favorable decisions in those cases.

Though Robson declines to comment on that scenario, he said if he had "a bet today" on what will happen to those applications, "I would say I think they will be, in the main, approved. I happen to think that's what ought to happen across the board." But he agrees that it also subjects the carriers to a kind of ad hoc deregulation. "One of the disadvantages I see in not doing your regulatory change across the board is that you put the people in the system now in a situation where they get sort of slammed from behind and they don't have the corresponding freedoms to competitively respond."

Although he has declined throughout his tenure to talk about policy and personality differences among board members, the deep divisions - often along party lines - were obvious at last week's meeting, called to discuss one of Robson's pet projects, a new and more stringent code of conduct for board members and employees. Robson had initiated a review of the board's 10-year-old and often-criticized rules in mid-1975.

The two Democrats on the board - G. Joseph Minetti and Lee R. West - voted against the new code. Although the proposal that resulted from the inquiry and subsequent revisions were submitted for public and staff comment three times since January, they both complained that action was premature and that at least one staff member had wanted additional time to comment on the final version drawn up.

"I've got to say I feel there's something questionable about a rush to adopt rules to apply to people staying here and living with them by those who aren't," West said pointedly at the meeting, suggesting the new ethical standards were being "railroaded" through.

Robson will be on his own starting tomorrow, when he becomes a visiting fellow at the American Enterprise Institute; he also has plans to do some teaching at the Yale School of Management. Beyond that, he says he has deferred talking to anybody about what he will do in the future, including his old law firm, until he had left the board, and consequently has not made permanent plans. "I think it's a good time in my life to examine other opportunities," he says, "if there are any."

Would he ever return to the government again? "Sure."