President Bush signed a tax law last week that will extend the "bonus depreciation" breaks that have been credited with boosting aircraft sales by as much as 30 percent. The law extends the "placed-in-service" date for business aircraft to qualify for bonus deprecation until Dec. 31, 2005. The break provides a real buyer incentive, said Ron Swanda, interim president of the General Aviation Manufacturers Association. "Without a doubt, this will stimulate jobs growth in our industry," he said. The tax break, which allows buyers of new business aircraft to deduct 50 percent of the plane's cost in the first year, up from 30 percent, had been set to expire at the end of 2004. The tax package, which is labeled as a jobs-creation effort, has been critiqued as a treasure trove for special interests and big business, with no apparent incentives for hiring workers. Mr. Bush signed the law on Friday while aboard Air Force One, forgoing the usual public ceremony.