Except as provided in this Code section, no state official or employee, when traveling by commercial air carrier on a first-class basis, shall be reimbursed for that portion of the first-class air fare which exceeds the amount of the fare of the next lowest fare for the flight on which such official or employee is traveling. This shall not prohibit the reimbursement for the entire cost of first-class air fare under any of the following conditions:
OCGA § 45-7-30