A nationwide alert has been issued for 17 members of the Afghan military who have gone AWOL from a Texas Air Force base where foreign military officers who are training to become pilots are taught English, FoxNews.com has learned. . . . A senior Defense Department official in Washington told Fox News he had no direct knowledge of the 17 men being AWOL. The official added that this is not the first time foreign trainees have gone missing, and said some cases in the past have turned out to be more of an immigration concern than a national security threat.