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Route Correction: Fix a Mistyped Destination

intermediate
📍 Route: KJFK → EGLL (initially mistyped as EGKK)⏱ ~4 minutes📊 10 steps🎓 Flight Plans & Routing

The destination is wrong on the RTE page. Overwriting a field you already filled is a distinct skill from filling it.

What this scenario covers

Correcting an entry on the 737 means typing the new value into the scratchpad and line-selecting it over the old one, then executing. Because the change is staged, you get to see the modified route before it becomes real — and can erase it if it is not what you wanted.

The scenario has you make the mistake yourself and then repair it twice over — once on the destination, once on the company route code that still named the old one — because a correction almost never stops at the field you noticed.

How it applies in flight ops

Reroutes and destination changes are ordinary events: weather, a diversion, a slot, a tail swap. What makes them safe is that the crew treats a changed field as invalidating everything downstream of it until they have looked.

The cross-check is against the source document — the OFP or the clearance — and never against memory. A well-formed wrong entry is indistinguishable from a right one on the screen.

Start this scenario

Opens the SimTuts 737 CDU trainer with “Route Correction: Fix a Mistyped Destination” already running, so you can walk through it step-by-step on the simulated keypad.

Open trainer →

Step-by-step: Route Correction: Fix a Mistyped Destination

  1. Press the RTE page key to open ROUTE.

    Real-world scenario: dispatch sends a corrected OFP, or ATC issues a reroute clearance. You need to overwrite an entry that's already there. The 737 CDU requires CLR-and-retype, not edit-in-place.

  2. Type KJFK and press 1L for ORIGIN.

    Same as a normal route entry. The mistake comes next.

  3. Now type EGKK (London Gatwick) and press 1R for DEST. (We'll fix this in the next step — this is the wrong airport.)

    EGKK is London Gatwick, not Heathrow. A common mistake when copying from an OFP — adjacent codes, similar destinations.

  4. You realise the OFP says EGLL, not EGKK. To fix it: press CLR (or Backspace) until the scratchpad is empty, type EGLL, then press 1R again to overwrite DEST.

    On the 737 CDU there is no edit-in-place. Pressing an LSK with new scratchpad content overwrites whatever was there. This is how every correction works on the box, including ATC reroutes. Note what you did NOT do: the DEL key will not empty ORIGIN or DEST — the FMC answers INVALID DELETE, because a route must always have both ends. Overwriting is the only way.

  5. Type BAW178 and press 2R for FLT NO.

    Sanity check — fixing one field doesn't reset the others. The flight number, CO ROUTE and any other entered data persist through a correction.

  6. The OFP also carried a company route code, and it was built for the old destination. Type KJFKEGKK1 and press 2L for CO ROUTE.

    This is the part that bites in the real aeroplane. A correction rarely touches one field. The company route code names both ends of the flight, so the moment the destination changed, this code became stale — and nothing on the CDU will tell you, because it is a perfectly valid string.

  7. Fix it the same way: type KJFKEGLL1 and press 2L again to overwrite CO ROUTE.

    The same overwrite works on a different field, which is the rule worth carrying away: on the Boeing CDU, correcting anything is "type the right value, press the key it belongs to". There is no cursor, no insert mode, and no field you edit character by character.

  8. Now commit the corrected route. Press 6R (ACTIVATE), then press the EXEC key.

    Until now every correction you made was just text on a page — the FMC had nothing active to correct. ACTIVATE stages the route and the lit EXEC key commits it. This step has no Airbus counterpart at all, and it is the one that catches pilots coming across: on the A320 an entry takes effect as you make it; here it takes effect when you press EXEC.

  9. Press 6R to open PERF INIT, then type 52 and press 5L for COST INDEX.

    Cost index balances fuel burn against time. The value comes from dispatch on the OFP, and it is worth entering here because it is the other thing a re-issued OFP commonly changes — a longer routing sent at a different cost index is a very ordinary day.

  10. Read it back. Press the LEGS key and confirm the route shows KJFK and EGLL, with no EGKK anywhere.

    The read-back is the whole point of the exercise. A correction you made but did not verify is indistinguishable from one you thought about and forgot, and the LEGS page is where it shows. Check the title too: ACT RTE 1 LEGS means everything is committed — MOD would mean something is still staged and the aeroplane is not flying what you are looking at.

What to take away

  • Overwrite by line-selecting the new value over the old, then EXEC.
  • The staged modification lets you see the change before committing.
  • Everything downstream of a changed field needs re-checking.
  • Verify against the paperwork, not against what you intended to type.

The rest of Flight Plans & Routing

Background reading

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