AIRLINES

Major Carriers Extend Northwest’s Fare Cuts: The action affects a summer sale begun over the weekend by Northwest Airlines and increases the discounts on some routes. American Airlines shortened the advance-purchase time from 30 to 14 days, making the sale applicable to flights in early May, a move matched by several major airlines. American also offered steeper discounts on coast-to-coast flights through mid-June. United Airlines said it will be competitive with the move, while other airlines said they were studying it. The latest sale gives passengers only until April 27 to buy tickets. The prices apply to destinations in Canada and all states except Alaska. Trips must be completed by Sept. 12. The best coast-to-coast prices are available for trips taken before June 16.