Northern Virginia from the older National Airport (a focus city for American Airlines) are restricted for distance, frequency, and flight paths due to the proximity to federal facilities, Dulles is the region's second busiest airport in both passenger loadings and aircraft movements, and the sixteenth-busiest airport in the United States by takeoffs and landings in 2007. Dulles is the region's primary international gateway, serves as a hub for United Airlines, and has recently improved its low-cost carrier offerings with the addition of multiple flights by Southwest and JetBlue. Commuters are served by the Washington Metro subway and the Virginia Railway Express, a
Avery Dulles of Notre Dame, the Catholic University at Leuven, Yale University, and St. Joseph's Seminary, Dunwoodie. He was the author of over 700 articles on theological topics, as well as twenty-two books. In 1994, he was a signer of the document "Evangelicals and Catholics Together." Past President of both the Catholic Theological Society of America and the American Theological Society, and Professor Emeritus at The Catholic University of America, Dulles served on the International Theological Commission and as a member of the United States Lutheran/Roman Catholic Dialogue. Dulles was critical of dual-covenant theology, especially as understood in the U.S. Conference of