Reports surfaced yesterday that Secretary of Defense Caspar W. Weinberger will recommend a totally unexpected solution to the vexing problem of basing the new MX intercontinental ballistic missile: putting them aboard converted jet transports for aerial launching.

The reports, from government and industrial sources, were denied immediately by Weinberger, who said he has made no decision on the controversial question of where and how the MX will be deployed.

"There's a great many rumors floating around, and this is one of six," Weinberger said. "I haven't decided anything or made any recommendation yet."

Nevertheless, sources on Capitol Hill, from within the administration and among defense contractors provided similar accounts of a plan they said weinberger will recommend soon. The plan involves placing 100 MX missiles aboard a new fleet of 100 giant C5A Air Force jet transports. m

This essentially would do away with land basing of 200 MX missiles and 4,600 protective shelters spread throughout Utah and Nevada. That solution was adopted by the Carter administration, but has come under fire from some of President Reagan's otherwise staunchest supporters in the West.

The president has indicated that he has serious reservations about the land basing of the MX, even though the Air Force favors it.

Under the new plan a single MX missile, enclosed in what is called a launch capsule, would be put on each modified C5A. These planes would be kept on alert on runways at a string of bases, some of them dnew ones, in the central part of the United States. Upon warning of attack, the planes would be launched within minutes and therefore theoretically would be invulnerable to a Soviet first strike.

The initial force of 100 planes and missiles is described by sources as an interim solution which would lead eventually to deployment of a larger airborne force in a new airplane nicknamed "Big Bird," which would be especially designed for the 250,000-pound MX missile and capsule combination.

The Air Force is known to object strongly to this plan, which had been studied and rejected twice before by Air Force leaders and the Carter administration. Sources said yesterday that a new task force has been formed within the Air Force to oppose the prospect of such a recommendation going to the president, and will make its case to Weinberger next week.

There were suggestions from some sources yesterday that the Air Force was behind the reports that were circulated in a possible effort to overturn the plan.

Throughout the lingering debate about what to do about the MX, officials have stressed repeatedly that there is no non-controversial answer to the basing problem. Each proposal has a wide range of supporters and opponents. In the case of the pending land-basing proposal, opposition had been expressed by Reagan's former national campaign chairman, Sen. Paul Laxalt (R-Nev.), and by the Mormon church.

However, the airborne-basing plan has re-emerged because it seems to have important economic, political and military advantages, at least in the short run. The administration is known to be seeking defense economies approaching $10 billion a year in order to carry out Reagan's promise to balance the budget by 1984.

The airborn plan would be less costly in the next few years. However, many specialists say that it would be more expensive ultimately than any of the alternatives.

Initial estimates are that it would cost $15 billion just for new bases and other facilities, not counting the cost of the planes or the missiles. New bases would be needed, specialists said, because many existing bomber bases are near the coast, and the idea would be to keep the new planes as far away as possible from Soviet missile-carrying submarines.

The future Big Bird program envisions keeping many planes in the air at all times, adding further to the operating costs of the system.

One political advantage of the airborne plan is that it would avoid the environmental controversy that is certain to continue surrounding any proposal for a land-based MX system. On the other hand, the building of many new bases could lead to similar political opposition.

Militarily, the airborne plan offers the possibility that more American weapons would be able to escape a Soviet first strike. Furthermore, the missiles clearly would not be a first-strike weapon, and thus would not threaten the Soviets to the same degree as land-based missiles.

On the other hand, military specialists also say they believe that no matter where the plans are based, Soviet nuclear weapons exploded over the central United States would keep them from taking off.

The specialist also say that the planes would be able to stay aloft only for a few hours, so decisions to fire the missiles would still have to be made rapidly

Finally, there are those who argue that the United States would be taking a major risk by introducing potential communications problems into two portions of the U.S. nuclear retaliatory force.

It is difficult to communicate with missile-firing submarines under some conditions, and now the United States would have to worry about disrupted radio communications with missile-carrying airplanes.

Diplomatically, the proposal is potentially explosive. Washington has pressed its Nato allies to accept new American-built Cruise missiles on their soil.

That plan is politically controversial in Europe, and any move by the Reagan administration to solve its domestic political problems by putting missiles in the air rather than on land would be likely to increase the prospects of European rejection of the U.S. missiles.

For this variety of reasons, the airborne plan is thought to fact serious obstacles in Congress if it is proposed. One source who favors the land-basing system said yesterday that he feared that the entire MX system could wind up being rejected if the airborne proposal is made.