Replan while choices remain

How do you compare continuing and diverting fairly?

Begin from the same current position, time, fuel and aircraft condition.

Use one current state

Record current position, actual time, usable fuel, aircraft condition and the relevant clearance. Build each candidate option from that same state. A destination option calculated from now cannot be compared fairly with a diversion fuel figure that starts at an earlier checkpoint or assumes an aircraft already at a different level.

For each option, calculate the connected remaining route, profile, time, fuel and required protection using the applicable method. Reassess suitability over the relevant time window, including approach/navigation capability, runway performance, weather and services. A short fuel figure does not establish a safe landing.

Compare usable margins

Predicted landing fuel minus the applicable required landing quantity gives a stated numerical margin, but margin alone does not rank every operational risk. An option with higher fuel margin can have worse weather or require a capability that is unavailable. Reject unsuitable options before comparing their residual margins.

A revised level or speed may improve one part of the plan and worsen another. Lower altitude can improve weather avoidance but increase fuel flow; a faster speed can reduce exposure time while consuming more fuel. Use connected performance data and state the trade-off.

Decide before the gate closes

Determine when a current option will cease to meet its requirements if the aircraft continues or delays. That is a useful decision trigger. Repeating the same comparison after the option has disappeared does not restore it. Use the relevant crew,ATC and operational-control processes without deferring a necessary safe-landing decision.

The laboratory compares two synthetic branch burns against the same current fuel and protected amount. It makes the maximum affordable burn visible, but does not establish aerodrome suitability or prescribe a route. Explain which candidate remains feasible and what changed from the original plan.

What makes a revised plan complete?

A complete update connects the new decision to calculations, communications and monitoring.

Propagate the chosen change

A diversion can change route, navigation capability, safe levels, speed, fuel burn,ETA, runway condition, landing performance and briefing needs. Update the affected fields using current evidence. The new plan must describe the aircraft’s actual configuration and the clearance it will fly.

A delay at the current aerodrome or in holding also consumes fuel and moves arrival into a later weather window. Calculate the remaining delay allowance from a protected plan rather than treating every kilogram above final reserve as freely expendable. The required decision criteria come from the current operational scheme.

Set the next check

After selecting an option, record the expected time and fuel at a near-term checkpoint. Compare actual performance there and reassess if the trend differs. A revised plan without a monitoring trigger can become obsolete in exactly the same way as the original.

Communicate the appropriate route, destination and fuel state through the applicable procedures. An updated internal calculation is not the same as an ATC clearance, an amended ATS message where required or a confirmed operational coordination. Preserve those states distinctly.

Explain the decision in one causal chain

For example: actual GS is lower than planned; remaining flight time and burn rise; predicted landing margin falls; a suitable nearer diversion preserves the required quantity; a new checkpoint will test the revised burn. This explanation links evidence to action and to the next verification.

The final exercise keeps the arithmetic synthetic and fully stated. It does not claim to replace a flight manual, current AIP, operational approval or commander’s decision. The learning objective is to reconstruct a defensible plan from changed facts and show how each animation or number contributes to that reasoning, rather than merely producing a visually complete flight-plan form.

Can you explain and apply the mechanism?

Four original questions. Work from the stated facts, then compare your reasoning with the explanation.