ATS flight plan and OFP do not agree: can the flight depart?
A Boeing 737-800 is scheduled Auckland (NZAA) to Christchurch (NZCH). The operational flight plan shows: taxi 200 kg; trip 4,100 kg; contingency 205 kg; alternate Dunedin 1,000 kg; final reserve 1,300 kg; take-off fuel 6,805 kg; endurance 3:05. The ATS flight plan filed shows: EET 1:15; endurance 2:45; alternate NZDN; route 'AA B333 DUMBA', where DUMBA is not in the aircraft navigation database; no company holding allowance. The Christchurch TAF is fine, but the Dunedin TAF has TEMPO 300 m fog for two hours around ETA. The company requires an alternate to be above minima for ETA ±1 hour. The captain says the ATS flight plan is only a notification and can be fixed in the air.
1. Identify the errors and explain why each matters for the ATS flight plan and operational flight plan.
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Errors and significance:
- Endurance mismatch. The OFP total fuel endurance is 3:05, but the ATS flight plan says 2:45. The ATS figure understates the usable fuel by 20 minutes. It must reflect the actual total fuel endurance after the final load is known, not simply exceed the EET.
- Unsuitable alternate. Dunedin is forecast below minima for ETA ±1 hour, so it does not meet the company alternate requirement. A suitable alternate must be nominated, with fuel recalculated. If Invercargill is used and requires 1,150 kg instead of 1,000 kg, take-off fuel becomes 6,955 kg and endurance about 3:10.
- Unknown route point. DUMBA is not in the navigation database. If it is not a valid ATS route point, the route is not reproducible by the aircraft and may be rejected or cause a clearance problem. A valid waypoint or re-route must be filed.
- No holding allowance shown. The OFP fuel may include no company holding allowance, yet the ATS flight plan must be consistent with the fuel actually carried.
The ATS flight plan is not merely a courtesy message; it supports ATC coordination and SAR alerting. It must be accurate before departure.
2. Can the flight depart as currently filed? State the actions required.
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No. The flight should not depart with the ATS flight plan in its present form. Required actions before departure:
- Select an alternate that is forecast above minima for ETA ±1 hour; recalculate alternate fuel and take-off fuel. With Invercargill at 1,150 kg, the take-off fuel is 200 + 4,100 + 205 + 1,150 + 1,300 = 6,955 kg.
- Amend the ATS flight plan endurance to match the OFP figure, about 3:10, not 2:45.
- Replace DUMBA with a valid database/ATS route point or file a corrected route.
- Recheck that the OFP and ATS flight plan agree on destination, alternate, EET, route and endurance.
If these changes cannot be made before the slot, delay the departure. 'Fixing it in the air' is not acceptable for a known flight-plan discrepancy; ATC and SAR may act on incorrect endurance or alternate data. Once amended, the flight may depart with the corrected fuel and documentation.