Hoping to stave off a shortage in air traffic controllers caused by an expected wave of retirements, the FAA will hire 12,500 controllers over the next 10 years and improve training so that candidates can become fully certified more quickly. More than 11,000 controllers are expected to leave the agency between now and 2014. The additional 1,500 new hires take into account increases in traffic volume, an expected 5-percent training failure rate and the still higher than normal retirement rates beyond 2014. Improvements in classroom training, increased use of simulators and more efficient on-the-job training can compress the full training process from between three and five years to between two and three years, the agency said.