Four Virginia congressmen appealed yesterday to Transportation Secretary Elizabeth Dole to close a loophole in the National Airport curfew that has allowed American Airlines to schedule two late-night flights there beginning Wednesday.

Sens. John W. Warner and Paul S. Trible and Reps. Frank R. Wolf and Stan Parris, all Republicans, said in a letter to Dole that the flights are "contrary to the wishes of the Washington community and a violation of the spirit and intent" of the federally owned airport's 1981 noise policy.

Noting that the new late-night flights will not count against airlines' daytime landing quotas at National, the legislators also expressed concern that carriers may circumvent a system intended to control traffic and congestion there.

Dole was urged to block American's plans and amend the Federal Aviation Administration's noise standards to stop other airlines from using the relatively new and quiet DC9 Super 80 to make late-night landings. The 142-passenger plane is permitted to make the flights because it is quieter than all other commercial jetliners and makes less noise than the 10 p.m. curfew allows. "We believe the policy should be clarified in such a way that its original intent, to preclude the late-night operation of air carrier aircraft, be made inviolable," the letter said.

The legislators also wrote to American Airlines President Robert L. Crandall asking him to reconsider the flights. Spokesmen for Dole and Crandall declined comment yesterday.

The letter to Dole said that many area residents supported the proposed noise policy in 1981 with the understanding the standards would effectively ban against all nighttime passenger jet operations.

Federal Aviation Administration officials have said that they did give these assurances, but based their promises on test results showing that the DC9-80 would be too loud for National. Later tests indicated the jet was quieter than expected and would be able to land, they said.