The JTACs have a high operational tempo - with frequent deployments overseas into combat zones. While they sign up for the Air Force they spend most of their time with the Army on combat operations. The frequent deployments have caused a high rate of attrition - many JTACs are opting out and leaving the service. This attrition rate causes a perpetual shortage of JTACs and a lowering of the overall experience level.
There are limited opportunities for personnel of other services to achieve a JTAC rating. One is the Special Operations Terminal Attack Controller Course (SOTACC) which teaches special operations personnel from the Army, Air Force and Marine Corps the conduct of close air support missions and fully certify them as qualified Joint Terminal Attack Controllers (JTAC). However, the SOTTAC course has a limited capacity to train personnel - so most special operations teams must rely on a JTAC provided by the Air Force.
The latest 'friendly fire' incident in which five Army personnel were killed (mid-2014 in Zabul province) in a Special Forces operation is partly the result of a JTAC who had a mediocre record of performance. In addition, the B-1B crew has been grounded. Read more in "Attrition: A Rare Friendly Fire Incident Explained", Strategy Page, November 14, 2014.