Military members who travel on official duty (either temporary duty travel or permanent change of station), can request mileage reimbursement for their travel by "personally owned conveyance" (POC), instead of a government purchased an airline ticket.
This offers flexibility in scheduling but the reimbursement process can be a bit convoluted and vary depending on whether your travel is for temporary duty (TDY) or a permanent change of station (PCS). It's best to verify what the rates are before you travel to ensure that the cost and potential wait time for reimbursement are worth it.
Temporary Duty (TDY) Travel
For both uniformed personnel as well as DoD civilian personnel, there are some rules dealing with POC use if travel by POC is not in the Government's interest (namely limits on payment). The best rule of thumb is that the method of travel needs to be specifically mentioned in your orders if you wish to be assured of reimbursement.
Uniformed personnel may request (or commands may provide) actual expense reimbursement instead of the mileage for TDY travel.
Under federal law, TDY mileage rates are based on cost data collected by the General Services Administration (GSA), and even then, the TDY mileage rate can never be higher than the rate allowed by the Internal Revenue Service.
In addition to the mileage rates, military personnel members receive a per diem for each day of travel. The per diem amount is separate from the travel reimbursement and is paid separately.
Permanent Change of Station (PCS) Travel
Rates for PCS travel, known as MALT (Monetary Allowance instead of Transportation), are different (lower) than TDY travel. It is because TDY travel rates are specifically designed to reimburse the military the member for traveling on official duty.
The MALT/PCS mileage rates do not reflect the price of gasoline. TDY mileage rates, on the other hand, are based on the costs to operate a vehicle (gasoline, insurance, etc.) and are intended to reimburse the expense of using a POC for the official government travel.
Remember, the reimbursement rate is based on a per car calculation, not per person.
In addition to the mileage rates, military personnel and their dependents receive a per diem for each day of travel. Generally, 1 day of travel time is allowed for every 350 miles of official distance of ordered travel. If the excess is 51 miles or more after dividing the total number of miles by 350, one additional day of travel time is allowed. When the total official distance is 400 miles or less, 1 day's travel time is allowed.
When traveling via commercial airline (or other means of travel such as bus or train), the per diem for the member is computed under lodgings plus at the rate for the new permanent duty station, or the rate for the delay point if the member stops overnight. Per diem for the dependents is 3/4 of the member’s applicable rate for each dependent 12 years old or older and 1/2 of the member’s rate for each dependent under 12 years.