The House of Representatives has approved legislation that would allow a Chino air museum to keep two Soviet MIG fighter jets and a third plane bought in violation of a law prohibiting importation of military aircraft from Warsaw Pact nations. The proposed amendment to the 1990 Foreign Assistance Act would allow museums and other educational institutions to import warplanes from Poland or Hungary if the craft are disarmed and at least 25 years old. The Planes of Fame Air Museum in Chino last summer purchased MIG-15 and MIG-17 fighter jets from a Los Angeles broker who imported them from Poland. They quickly became a hit with museum patrons. But U.S. Bureau of Alcohol, Tobacco and Firearms agents said the importation of the obsolete, swept-wing jets violated the law.