A proposed 3.5-mile extension of the Dulles Access Highway that would link Washington and Dulles International Airport via Interstate Rte. 66, won enthusiastic enodrsements yesterday from most speakers at an all-day hearing in McLean.

But a toll road that Virginia officials are planning to build parallel to the airport road was bitterly attacked by many of the more than 50 speakers, including groups still fighting the controversial I-66 route.

Fairfax County officials, however, voiced strong support at the Federal Aviation Administration hearing for both the highway extension and the toll road, a concept previously endorsed by the FAA, which owns the Dulles highway.

John F. Herrity, chairman of the Fairfax County Board of Supervisors, and two other supervisors, Martha V. Pennino and John Shacochis, argued that the new highways will help end traffic jams around the popular Tysons Corner Shopping Center. The roads will speed traffic between Washington and the growing Reston area and will prompt major industrial and commercial development along the corridor, they said.

McLean Citizens Association president Philip Zanfagna said most area residents support extending the irport highway, a project for which the FAA has owned land more than 20 years ago. But he said "we have misgivings about some adverse impacts of the highway and some aspects of the environmental impact statement."

The hearing yesterday was required under federal law to assess the impact the project will have on the area. A final environmental statement is expected to be completed by the FAA late this spring.

The FAA built the airport highway as a limited access road for automobiles headed to the airport, located along the Fairfax-Loudoun County line. It has long planned to extend the road to I-66 inside the Capital beltway and at the same time agreed to allow Virginia to place a parallel road inside the highway's right-of-way, if it wished.

Legislation that would create the toll road now is moving through the Virginia General Assembly.

The environmental groups yesterday questioned the need for extending the airport access road at all, arguing that sufficient airport traffic to justify the road is not expected for at least another decade. The group also criticized the Faa/ for failing to consider the full impact of air pollution, noise, and traffic both in Virginia and the District that will be generated by the extension and the toll road.

The roads "won't speed air travelers into anything but a huge I-66 traffic jam," said Elizabeth Horvath of the Northern Virginia Conservation Council. There are "two huge government agencies ganging up on us" to force construction of highways, Horvath said.