Every witness who spoke before the House aviation subcommittee yesterday agreed that National and Dulles International airports are badly in need of expensive improvements, but they agreed on little else.

"There's just no question, help is needed," said Rep. Norman Y. Mineta (D-Calif.), chairman of the panel that yesterday concluded two days of hearings on a plan to relinquish direct federal control of the facilities.

"We ought to be ashamed of ourselves for allowing this to happen," said Rep. Norman Sisisky (D-Va.), who characterized the airports' condition as "desperate."

What became increasingly unclear during the hearings is how the money to finance the improvements -- estimated to be as much as $1 billion -- will be raised. The Reagan administration wants to see a regional authority take control of the two airports, and the Senate approved a bill this spring to create one.

Mineta, saying the House would refuse to yield control, is pushing alternative legislation calling for a federal corporation to run the airports.

Maryland officials said yesterday, as they have at every hearing, that the regional authority would place their state-owned Baltimore Washington International airport at a competitive disadvantage. Community activists who live near National Airport urged the subcommittee to force any new airport agency to adopt strict noise standards that the Senate-passed bill lacks. Airline officials told the committee that noise guidelines are no longer necessary.

A representative of Old Town Yacht Basin Inc., apparently invoking a 1791 federal statute, told the panel that it had no right granting Virginia "its ill-conceived claims" to land that belongs to the District of Columbia.

"It's noted in law from the days of George Washington," said John Chapman Gager. "No public buildings should be built on the Virginia side of the Potomac."

In other words, yesterday's session was typical of the decades-old argument about moving National and Dulles -- the only two commercial airports owned by the federal government -- out of the federal bureaucracy.

"The first Hoover Commission recommended incorporation of the airports as business enterprises in 1949," Harold Seidman, a former federal budget official, told the panel yesterday. "Since that time incorporation has strongly been recommended by Presidents Eisenhower, Kennedy and Johnson and legislation was introduced in the Congress under each of their administrations."

The idea reemerged two years ago when Transportation Secretary Elizabeth Hanford Dole appointed a commission to devise a way to transfer the properties from federal control. She has said repeatedly that the federal government should not be in the business of running airports.

Dole had little trouble getting the bill through the Senate, but many House members appear to be opposed or indifferent.

Much of yesterday's testimony attempted to assess whether a federal corporation could have the flexibility to raise money as quickly as an independent authority. Proponents said that it could and others said that it could not.

"It has been clear for many years that the national capital airports meet all the criteria for a government corporation," said Alan L. Dean, a former Transportation Department official.

"A federal corporation just won't be able to respond fast enough to the urgent capital needs at both those airports," said Sen. Paul S. Trible (R-Va.), who sponsored the bill that passed the Senate.

The subcommittee is expected to take action on either the administration bill or the corporation concept within the next month.