(a) travel by air: up to the maximum cost of an economy class ticket at the time of the  reservation;  (b) travel by boat or rail: up to the maximum cost of a first class ticket;  (c) travel by car: at the rate of one first class rail ticket for the same journey and on the  same day;  II.22.4  The contracting authority reimburses subsistence expenses on the basis of a daily subsistence  allowance as follows:  (a) for journeys of less than 200 km for a return trip, no subsistence allowance is payable;  (b) the daily subsistence allowance is payable only on receipt of supporting documents  proving that the person concerned was present at the destination;  (c) the daily subsistence allowance takes the form of a flat-rate payment to cover all  subsistence expenses, including meals, local transport including transport to and from  the airport or station, insurance and sundries;  (d) the daily subsistence allowance is reimbursed at the flat rates specified in Article I.5.3; (e) accommodation is reimbursed on receipt of supporting documents proving the necessary  overnight stay at the destination, up to the flat-rate ceilings specified in Article I.5.3. II.22.5  The contracting authority reimburses the cost of shipment of equipment or unaccompanied  luggage if it has given its prior written approval for the expense.  II.23.1  If an amount is to be recovered under the terms of the FWC, the contractor must repay the  contracting authority the amount in question. (a) by offsetting them against any amounts owed to the contractor by the Union or by the  European Atomic Energy Community or by an executive agency when it implements the  Union budget; 37  If the contractor does not pay by the due date, the contracting authority may, after informing the  contractor in writing, recover the amounts due:  If no observations have been submitted or if, despite the observations submitted, the contracting  authority decides to pursue the recovery procedure, it must confirm recovery by  formally notifying  a  debit note to the contractor, specifying the date of payment. The contractor must pay in accordance  with the provisions specified in the debit note.  Before recovery, the contracting authority must  formally notify the contractor of its intention to  recover the amount it claims, specifying the amount due and the reasons for recovery and inviting the  contractor to make any observations within 30 days of receipt.  In addition, the contracting authority reimburses travel outside Union territory if it has given its prior  written approval for the expenses.  II.23 RECOVERY  II.23.2 Recovery procedure 