President Reagan, apparently still hoping to find an alternative to the multi-silo, land-based system for the MX millile, was told today by two leading Republican congressional defense experts that that is exactly the system they favor.

Senate Armed Services Committee Chairman John G. Tower (R-Tex.) and Rep. William L. Dickinson (R-Ala.), the ranking Republican on the House Armed Services Committee, spent more than 90 minutes over lunch with the president.

Afterward they told reporters that they oppose basing the MX in aircraft or scrapping it in favor of a so-called "common missile" that could be used by both the Navy and the Air Force.

Tower appeared to pronounce the airborne MX dead. He said he doesn't think "very much serious consideration" is being given to basing the MX abroad a new fleet of transport planes.

The Reagan administration, with Defense Secretary Caspar W. Weinberger playing the leading role, has been seeking a deployment for the MX other than the Carter administration's proposal for moving the missiles among a large number of silos dug in Nevada and Utah.

Reagan invited the two legislators here because they have an understanding of "the political reality" as well as the technical problems surrounding the MX, Dickinson said.

"We were invited. We didn't ask to be seen," he said, although earlier White House deputy press secretary Larry Speakes had said the meeting flowed from a request by the legislators.

It seemed clear that the political realities Tower and Dickinson presented in Reagan's penthouse suite at the Century Plaza Hotel gave the president no comfort.

Reagan opposes digging the roads and silos for a deceptive basing system on environmental and political grounds. The president's closet Senate adviser, Paul Laxalt of Nevada, is firmly against it, as is the Utah-based Mormon church.

The president said during his election campaign that he was unenthusiastic about a plan that would chew up so much of the land in those two states. However, despite his reasons for opposing the land-based plan, he has been unable to find another method of basing the system that wins support from the Air Force or key defense leaders on Capitol Hill.

Reagan, who talked with reporters very briefly before meeting with Tower and Dickinson, said only: "We've made no decisions. That's why we're having the meetings. Really, I'm not snowing you."

The president was asked why his administration's deliberations on the MX were falling behind schedule. "These things take time," he replied.

Presidential counselor Edwin Meese III interjected that the administration has not fallen behind schedule. Meese has promised a decision within four weeks.

After the meeting, Dickinson said the president had not indicated what he is going to do.

Asked where a land-based, deceptive MX could be placed if not in Utah and Nevada, Tower and Dickinson said they were not recommending sites, but only telling Reagan that the huge missiles should be on land in order to preserve a triad of strategic nuclear weapons: missiles on nuclear submarines, bombs in B52s, and the land-based missiles.

"I believe in the preservation of the land-based leg of the triad," Tower said. To explain his opposition to a common missile, he cited sacrifices of range and payload that would be required to produce missiles small enough to be used on submarines as well as on land.

Dickinson said $3 billion has been spent on the MX already, money that would be wasted if the missiles are scrapped now. Abandoning the MX also would cost the administration time in its effort to close what it says is an existing "window of vulnerability" during which the Soviet Union has a military advantage over the United States.

Tower and Dickinson were even blunter in their rejection of the aircraft-based plan, which Weinberger had been reported until recently to favor. The plan is strongly opposed by the Air Force.

Dickinson said such a plan would not win congressoinal approval and would be an inadequate deterent.

"We looked at various strategic options and discussed them at some depth," Tower said of today's meeting. Asked when the administration stands, Tower replied: "I don't think you could say the administration is coming around to any specific view now. I think the president is very carefully examaining the options."