The Joint Travel Regulations (JTR) are applicable to uniformed members of the seven uniformed services ( i.e., Uniformed Members of the Army, Navy, Air Force, Marine Corps , Coast Guard, National Oceanic and Atmospheric Administration Commissioned Corps, and
Public Health Service Commissioned Corps), DoD civilian employees and others traveling at DoD expense. For DoD civilian employees, the JTR's authority is primarily derived from U.S.C. Title 5 statutes, General Service Administration's (GSA) Federal Travel Regulation (FTR), and the Department of State's Standardized Regulations.
Quoted from the Defense Travel Management Office Joint Travel Regulations webpage.
