United Airlines asked the city of Chicago for a $25 million subsidy to defer costs of moving to the recently renamed Willis Tower, a city alderman said. Second Ward Alderman Robert Fioretti said the airline would relocate about 2,500 employees to the recently renamed 110-story building that was formerly named the Sears Tower after Sears & Roebuck, its first primary tenant. Rita Athas, executive director of World Business Chicago, said, the collateral benefit to all the small businesses that surround the tower make an investment in the airline's move worthwhile. An official with the mayor's office said the city was working on a final package that ensures the city is competitive with the other locations that United is looking at. United is likely to rent about 450,000 square feet in the building, more than three times the amount of space the Willis Group Holdings Ltd.