At least two commercial developers, unsuccessful in their attempts to win changes in the Fairfax County master plan, intend to file rezoning applications anyway in what could evolve into an important challenge to the county's land-use controls.

The applications would almost certainly be turned down since they would not comply with the county plan. The developers' strategy, according to industry sources, would then be to file suit, putting the decision into the hands of the Virginia courts, which historically have been sympathetic to property owners' rights.

NV Cos., owner of a 98-acre tract north of Leesburg Pike (Route 7) and northwest of the Dulles Toll Road, plans to ask Fairfax to rezone that land from residential to commercial to allow construction of a low-rise office park, sources close to the firm said.

The rezoning will seek basically the same office plan that was rejected by the county planning board as part of the county's current plan-amendment process.

And Robert Thoburn and his son, John, on Thursday confirmed that they plan to file for rezoning of approximately 62 acres on the northwest corner of the Dulles Toll Road-Hunter Mill Road interchange. The land is zoned for residential use but the Thoburns will be asking for commercial zoning.

The application "will be filed within a month," John Thoburn said. Details of the proposed office park are not yet available. Sources close to NV Cos. said the filing of the rezoning along Rt. 7 "is imminent."

During the past month of heated debate over land use changes in these two areas, residents turned out en masse to oppose the proposals.

The Thoburns' attorney, Grayson Hanes, told the county planning commission in April that his client intended to file a rezoning application and sought to withdraw a plan amendment change for the northeast corner of the interchange, where Thoburn owns a large chunk of land. The planning commission refused that request.

Thoburn said an application for a commuter parking lot to be built on "about 100 acres" on that northeast corner tract would be filed later. But that will be a "separate application," he said. "There is already some support in Reston for such a proposal," Thoburn said.

He said the parking lot could be used for carpools and buses. Buses, he said, would have a straight shot from the parking lot into the east Falls Church Metro station, which is set to open in 1986.

Even though both NV Cos. and Thoburn had asked Fairfax County's planning commission to recommend that the County Board of Supervisors approve the land-use changes that would have facilitated the rezonings they will soon be filing, both NV and the Thoburns have decided to seek the rezonings without changes in the comprehensive land-use plan. Rezonings are generally tied to the county's land-use plan and approval of rezonings that don't conform to the plan would be highly unlikely, sources said.

Lawyers and other developers had predicted for several weeks that Thoburn and NV would seek rezonings as soon as the planning commission's expected negative votes were cast against their application for land-use changes.

If the rezonings are denied, those cases are likely to go to court, sources said. Sources close to NV Cos. have said for several months that the company is prepared to go to court to develop the 98 acres commercially. NV officials have argued that the land is not suitable for residential development because of its proximity to the Dulles Toll Road and Tysons Corner.

The NV Cos.' proposal was rejected by the planning commission because it represented a major westward expansion of the Tysons Corner commercial area, according to summaries of the commission meeting. Containment of the Tysons commercial boundaries has been a major issue in the ongoing efforts this year to amend the county land-use plan.

The Thoburn site on the northwest corner of the Dulles Road-Hunter Mill quadrant includes a small piece of land that is already designated by the master plan for industrial or commercial use. That designation predates construction of the toll road. Also abutting the site on the south side across Sunset Hills Road is land where the Virginia Department of Highways and Transportation is building a maintenance facility. South of the toll road along the same side of Hunter Hill as the Thoburn tract is an office park known as Parkridge.

Several attorneys representing other landowners and developers whose applications were denied by the planning commission -- and therefore will not come before the Board of Supervisors -- said their clients were also considering filing rezoning applications. But few were ready to talk about the possibilities. Several said they were "still conferring with their clients."

The filings by those two companies could set the stage for a return to the courtroom as the major forum for significant land-use decisions in Fairfax, said a prominent land-use lawyer.

County officials fear that court victories for either NV Cos. or the Thoburn applications would encourage other developers to try to circumvent the land-use process.

The county's comprehensive land-use plan was adopted in 1975 after many zoning cases were decided in courtrooms. Even though courts may often look with favor on residential neighborhoods, Fairfax has lost two key cases in the Tysons area. One led to construction of the largest existing office building in the Tysons area, Tycon Courthouse. The other led to construction of commercial town houses along the Vienna side of Old Courthouse Road. Some residents say construction of those town houses broke the line of demarcation between commercial development at Tysons and residential areas abutting Old Courthouse Road.

Because of what some critics have called "inconsistencies" in the way phases of the current land-use change process were conducted, there is also speculation that a successful court challenge to a rezoning springing from a denial of a land-use plan change could lead to an unwanted challenge in court to the county's land-use plan itself.

Lawyers representing owners of small parcels of land that were grouped by the county planning staff with large tracts as part of the plan amendment process this week said that procedures need changing. However, one said, the action by the staff might justify his bringing proposal back to the county for action next year. Land-use change proposals that are vetoed by the county planning commission cannot be brought before that body for two years, county regulations say.