My most recent employment as an aircraft mechanic for DOD(as contractor), we would fly commercial to maintain aircraft for various missions, or what we call a rescue det to for one of our aircraft that broke down somewhere where our maintenance crews were not.

All employees carried an American Express card(except abusers who had card privileges suspended) for all travel expenses.

Since we usually are bringing tools and safety equipment that can not be carried aboard, it gets checked in. If I get an overweight or extra bag charge, it goes on the AMEX and it is listed on my expense report and is reimbursed as an allowable cost.