American and United airlines announced 40,000 layoffs Wednesday as the U.S. aviation industry sank deeper into a crisis touched off by Sept. 11’s terrorist attacks. The parent company of American, the world’s largest airline, said it will lay off at least 20,000, or 14%, of its 138,350 workers. The cuts by AMR Corp. will affect American, TWA and American Eagle. United parent UAL Corp. matched the bad news little more than 90 minutes later, saying it would lay off 20,000 of its 100,000 workers. Just a day earlier, Boeing said it planned to trim thousands of jobs in the Seattle area. “This is not a ripple effect,” Rep. Jennifer Dunn, whose suburban Seattle district includes thousands of Boeing workers, told the Associated Press. “This is a tsunami.” In little more than a week, the attacks have cost the struggling U.S. aviation industry nearly 70,000 jobs and billions of dollars in vanished business. Airlines warn the layoffs could rise to 100,000 and are asking for $17.5 billion in federal aid to keep them from ruin. The air carriers initially had asked for $24 billion while the House had suggested $15 billion. Late Wednesday, the Bush administration said that it plans to ask Congress to give the airlines $5 billion in immediate aid. A decision whether or not to give another $12.5 billion in credits and loans to the industry would be made later.