The EXEC Light — Boeing's Commit Step

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📍 Route: DIRECT LFPG⏱ ~4 minutes📊 3 steps🎓 Foundations

The single biggest difference between the Boeing CDU and the Airbus MCDU: on the 737, nothing you type takes effect until you press EXEC.

What this scenario covers

Enter a change and the FMC builds it as a modification — the route becomes MOD RTE, the affected lines change appearance, and the white EXEC light illuminates. The active route is untouched. Press EXEC and the modification becomes the active route; press ERASE and it never happened.

This scenario stages a direct-to and commits it, so the MOD-to-ACT transition and the light are both visible in sequence.

How it applies in flight ops

The staging step is a safety feature: it gives the crew a moment to look at what is about to change, and it gives the other pilot something to cross-check before it is real. Airbus takes the opposite approach on many entries, applying them immediately.

The practical failure mode is a lit EXEC light nobody notices. The aircraft is flying the old route while the crew believes it is flying the new one, which is exactly the kind of divergence that gets caught by a scan discipline: EXEC light lit means something is pending, always.

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Step-by-step: The EXEC Light — Boeing's Commit Step

  1. Press the LEGS key to open the active route legs.

    LEGS shows the active flight plan as a sequence of waypoints. The title line reads ACT RTE 1 LEGS — "ACT" means this is the active route the aircraft is actually flying. Watch that title as you make a change.

  2. Stage a direct-to. Type LFPG into the scratchpad and press 1L to go direct to LFPG.

    You just MODIFIED the route — the title now reads MOD RTE 1 LEGS (not ACT), an amber EXEC* prompt appears at 6R, and on the real aircraft the white EXEC light on the CDU lights up. Crucially, the aircraft is NOT flying this yet. On the Airbus a change like this takes effect the instant you make it; on the Boeing it is only staged — a proposal — until you commit it. This is the difference that catches every pilot coming from the Airbus.

  3. Commit the change. Press the EXEC key to make the modification active.

    Pressing EXEC commits the staged modification: the title returns to ACT RTE 1 LEGS, the EXEC light goes out, and the aircraft now flies the direct-to. The rule to carry into every flight: any edit to the RTE, LEGS, HOLD, or DEP/ARR pages STAGES a change and lights EXEC — nothing happens until you press it. If you ever wonder "why isn't the plane doing what I told it", check the EXEC light: a lit EXEC means you have an uncommitted change.

What to take away

  • Changes are modifications until EXEC — the active route is untouched.
  • A lit EXEC light means something is staged and not yet flying.
  • ERASE discards the modification cleanly.
  • The staging step exists so the other pilot can check before it is real.

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