The EXEC Light — Boeing's Commit Step
beginnerThe single biggest difference between the Boeing CDU and the Airbus MCDU: on the 737, nothing you change takes effect until you press EXEC. Learn the MOD-vs-ACT route and the white EXEC light by staging a direct-to and committing it.
Start this scenario
Open the SimTuts 737 CDU trainer and select “The EXEC Light — Boeing's Commit Step” from the scenarios list to walk through it step-by-step on the simulated keypad.
Open trainer →Step-by-step: The EXEC Light — Boeing's Commit Step
- 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.
- 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.
- 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.