The nation’s fourth largest airline, Northwest Airlines has admitted it gave the government personal information on millions of passengers shortly after Sept. 11. The data was given to a research center at NASA that was working on a secret air-security project. Three months ago JetBlue Airways admitted it had turned over personal data. At the time officials at Northwest denied the airline had ever committed such a breach of privacy. The secret arrangement between NASA and Northwest was uncovered by the Electronic Privacy Information Center which had received documentation through the Freedom of Information Act.