All members of the active armed forces can apply for travel allowances and per diem over and beyond their basic military pay. Restrictions apply to the mode of travel and covered costs for food and lodging, so it pays to routinely check for current rates and regulations. Generally, military members who are changing locations temporarily on official duty or those who are relocating to a new duty station can request reimbursement.
The military pays for transportation for service members on airplanes, trains, cars, and ships. The mode of transit must be cost-effective (least expensive, most appropriate, and timely option). Temporary duty travel reimbursements as well as Permanent Change of Station (PCS) travel allowances are based on the cost-per-mile or number of passengers per vehicle or on transportation specifics spelled out in your orders.
Per Diem is a daily stipend paid to service members on official business or temporary duty at a different station than their assigned routine duty locations. Paid in addition to regular military pay, per diem includes lodging, food, and incidentals based on the location and local costs at the place of assignment.
Per diem can also fluctuate if the service member is lodged and dining in military housing and mess hall facilities or temporarily traveling off base. Overseas per diem rates are evaluated and adjusted each month. If you're in service in a location with costs that are not stipulated by prior assessments, military flat per diem rates apply.