THE BEST THING that can be said about the report of a Federal City Council task force on National Airport is that it could have been worse. The task force generally supported the proposals made by the Federal Aviation Administration to limit National's future growth. But given the ease with which the task force accepted practically all the arguments advanced by those who want few limits, or none, on National, it would not have been surprising if this report, too, had endorsed expansion forever.

The basic thrust of the report is that because National Airport is convenient for air travelers and because that convenience contributes to the efficient functioning of the federal government, other factors -- noise, dirt, congestion and even money -- have minor importance. With that as a starting point, it is easy to reject, as the task force did, almost every recommendation made about the future of this area's three airports by the National Capital Planning Commission, the Council of Governments and local citizens groups.

The song is one we have heard before: convenience is paramount -- you get used to the noise. It is the one that persuaded the FAA more than a decade ago to permit jets to operate at National, even though Dulles Airport was built by Congress to provide them a home. Its tune has been hummed quietly ever since as National's passenger load got bigger and bigger, while Dulles sat in solitary spendor in the Virginia countryside.

Of course, there are jarring notes. After stamping its approval on the FAA's proposals, which are supposed to mean a busier but less noisy National Airport, the Federal City Council said: "The proposed initial reduction in total jet flights may not make a significant difference in the perceived noise level on the Mall -- but it will keep it from getting worse."

Thanks a lot. We had thought the name of the game in Washington these days was to make the area a better place to live, not just to keep it from "getting worse."

The other recommendations of the task force reflect the same preference for the concerns of passengers as against those of residents. Put in a nighttime curfew, it said, but don't enforce it too rigorously. Don't worry about the perimeter rule that keeps long-haul flights out of the airport. And, but the way, spend about $200 million rebuilding National's facilities, including, perhaps, a parking garage for 7,000 cars, a two-level roadway and a new north terminal.

All of that is fine, we suppose, if you start from the premise that National is and always must be Washorroborated by other competent evidence, will not be allowed to stand, corroboration is peculiarly a matter for the jury, and sufficient corroboration may consist of either direct or circumstantial evidence which connects the defendant with