What has been referred to as the "Air Florida Disaster" is really only a symptom of the terminal disease that is National Airport. Conceived in propeller days and unable to fly in a jet age, this archaic and inadequate facility has outlived its usefulness. Its declining share of the metropolitan Washington air market is as irreversible as the burgeoning development beyond its boundaries. The region's commitment to outstanding alternative facilities at Dulles and BWI airports must inevitably prevail.

We could all gain by finally laying this transportation white elephant to rest, selling or leasing its 127 acres of water and 733 acres of land. The proceeds of such a transaction would be sufficient to fund an extension of the Metrorail system to Dulles Airport. Estimated by Metro officials to cost $380 million in 1980 dollars, this 161/2- mile extension is already in an advanced stage of planning. Estimated run time from Metro Center to Dulles is 35 to 40 minutes, probably at less cost than a taxi ride from Capitol Hill to National Airport. Convenience, the one argument defenders of National seem to have on their side, would be served, if measured by travel time, cost and comfort, rather than miles.

What is the current value of National Airport on the private real estate market? A fair indication is given by a look at its emerging Arlington County neighbor, the 116-acre Pentagon City development. Both have their own Metrorail stations and are large enough to be regarded as strategic mixed-use projects. Pentagon City is now zoned to permit the construction of over 2 million square feet of commercial and office space, 5,620 residential units, 2,000 hotel rooms, a nursing center, housing for the elderly and an 11-acre park.

The undeveloped, county-approved land at Pentagon City has a current market value estimated to exceed $120 million, according to information available from the Arlington County tax assessor. If fully developed at approved densities, this value would increase to approximately $800 million, generating taxes of $7.5 million annually.

Applying these statistics to National Airport, the value of the land would be in excess of $750 million. This would comfortably provide the funding to extend Metro to Dulles, leaving enough to demolish the runways and other deteriorated operational facilities and, as a bonus, leaving enough land and shoreline for a major waterfront-oriented recreational resource, incorporating perhaps a marina, aquarium, camping, bicycling and similiar park facilities. The developed portion of National Airport could constitute a veritable new town of 25,000 families and 9 million square feet of commercial and office space, at Pentagon City density.

The addition to Arlington's tax base and the impact of vastly expanded Metrorail service in Fairfax County are only illustrative of the windfalls that could accrue by virtue of the federal government's cashing in on its equity in National Airport. In fact, a host of federal, state and local beneficiaries could, and should, share.

Unlike the process of valuing National Airport, it is far more difficult to quantify the potential stimulus to our local economy, and Dulles and BWI operations, as well as the value of the tranquillity derived by those who live under National's air traffic pattern. Perhaps more important would be the assist to Metro in reaching its potential as a great urban transportation system.

We can only imagine the staggering political, jurisdictional and fiscal impacts of such an undertaking. Ten years would not be an unreasonable estimate of a minimum transition period, and it would probably take the likes of New York's late Robert Moses to pull it off. But other great cities have risen to similar challenges. One thing is clear: such a project could improve the lives of virtually everyone who travels or lives in the region. It could also save lives, as we recently learned.