A Rand Corp. study has found the Air Force could lose more pilots in coming years amid a hiring surge and salary increases by the nation's largest airlines.Military pilots are a likely target as American, Delta and United all boost pilot hiring during the next 20 years to replace their aging workforces, the California-based military issues think tank said in a study released Tuesday.Trisha Guillebeau, an Air Force spokeswoman in Virginia, said Thursday in an email that the pilot retention in the Air Force has declined for three consecutive years and resulted in a shortage of qualified pilots, which is most acute for fighter aircraft.