Diversion — Switch Destination Mid-Flight

Step-by-step: Diversion — Switch Destination Mid-Flight

1. You are airborne, mid-flight to LFPG. ATC has just told you to divert to EBBR (Brussels). Press RTE to open the ROUTE page.

   In flight, the FMC still has the original destination. You need to update DEST so the FMC recalculates fuel, time, and approach data for the new airport.

2. Type EGLL and press 1L for ORIGIN (the airport you departed from).

   Origin doesn't change on a diversion. The FMC needs it for distance/time calculations from your current position.

3. Now the diversion: type EBBR and press 1R to set DEST to Brussels.

   Updating DEST tells the FMC to replan everything from your current position to EBBR — fuel burn, ETA, approach charts, alternate selection. Real-world ATC will give you a vector toward the new airport while you do this.

4. On a real diversion you'd also need to load the EBBR approach. For now, press 6R to jump to PERF INIT and check fuel.

   Diversions are fuel-critical. The first thing real pilots do after updating DEST is verify they have enough fuel to reach the new airport plus reserves. PERF INIT is where that calculation happens.

5. Type 5.0 and press 4L to set RESERVES to 5.0 (in thousands of pounds — this is your final reserve fuel).

   Final reserve is fuel you must land with regardless of conditions — typically 30 min holding fuel for jets. Setting it on PERF INIT lets the FMC warn you if your remaining fuel will breach this minimum at the new destination.