Free Boeing 737 CDU Trainer
Practice programming the Boeing 737 CDU (FMC) in your browser. Follow guided scenarios with real-world routes and learn the PMDG 737 workflow — no flight simulator required.
This is the Boeing 737 NG CDU — for the Airbus A320 MCDU (different aircraft, different layout), switch trainers.
14 scenarios · updated 12 May 2026
How to use this Boeing 737 CDU trainer
Scratchpad: Type characters using the on-screen alphanumeric keys or your physical keyboard. Text appears in the scratchpad at the bottom of the CDU display — exactly like the real Boeing 737 NG.
Line Select Keys (LSKs): Press an LSK button to transfer scratchpad content into the corresponding field. Left LSKs (1L–6L) interact with left-side fields, right LSKs (1R–6R) with right-side fields.
Page keys: Use the dedicated page buttons to navigate between CDU pages — INIT REF, RTE, LEGS, DEP/ARR, PERF INIT, and more.
Example: Press RTE, type KJFK, press 1L for ORIGIN, then EGLL and 1R for DEST.
What is the Boeing 737 CDU?
The CDU (Control Display Unit) is the primary interface for programming the Boeing 737's Flight Management Computer (FMC). Pilots use it to enter routes, set performance parameters, configure approaches, and manage the aircraft's navigation throughout every phase of flight.
Learning CDU programming is one of the biggest challenges for new 737 pilots in flight simulators like MSFS 2024 and X-Plane — especially in detailed add-ons like the PMDG 737. This trainer lets you practise the key workflows — RTE, PERF INIT, and TAKEOFF REF — without needing to load the full simulator.
Boeing 737 CDU vs Airbus A320 MCDU
The Boeing 737 CDU and the Airbus A320 MCDU both program the aircraft's Flight Management System, but they look and behave very differently. This trainer simulates the Boeing 737 NG CDU — if you're flying the A320, use the A320 MCDU trainer instead.
- Naming: Boeing calls it CDU (Control Display Unit); Airbus calls it MCDU (Multipurpose Control and Display Unit).
- Display: Boeing is monochrome white/green; Airbus uses colour (cyan, green, amber, magenta).
- Page structure: Boeing uses IDENT → POS INIT → RTE → LEGS → PERF INIT → TAKEOFF REF. Airbus uses INIT A → F-PLN → PERF (with takeoff/climb/cruise/descent phases).
- Field labels: Boeing ORIGIN / DEST / FLT NO / CRZ ALT; Airbus FROM/TO / ALTN / FLT NBR / CRZ FL.
- Route building: Boeing enters VIA/TO pairs on RTE, then edits LEGS. Airbus uses F-PLN with airway search and discontinuity handling.
The underlying aviation concepts (cost index, V-speeds, OFP planning) are identical — only the interface differs. If you already know one, the other is easier to learn.
Guided scenarios
Each scenario walks you through a real-world route step by step. Start with the ROUTE page basics, then progress to a full short-haul setup with cost index, cruise altitude, and takeoff V-speeds.
- ROUTE Page Basics· beginner · 3 min
- London Heathrow to Paris CDG· beginner · 5 min
- Route Correction — Fix a Mistyped Destination· intermediate · 3 min
- Diversion — Switch Destination Mid-Flight· intermediate · 3 min
- CDU Pages Tour· beginner · 3 min
- Cost Index — What Does It Do?· beginner · 3 min
- TAKEOFF REF — V-speeds· intermediate · 3 min
- Assumed Temperature — Reduced Thrust Takeoff· beginner · 3 min
- Step Climb Mid-Cruise· advanced · 5 min
- REF NAV DATA — Navaid Lookup· intermediate · 3 min
- RTE Airway Entry & the "NOT IN DATABASE" Fix· intermediate · 4 min
- The EXEC Light — Boeing's Commit Step· beginner · 4 min
- Closing a LEGS Discontinuity· beginner · 4 min
- POS INIT — Aligning the IRS· beginner · 3 min
Frequently asked questions
Is this for Airbus or Boeing?
Boeing. This trainer simulates the Boeing 737 NG CDU (Control Display Unit). For the Airbus A320 MCDU, use the A320 MCDU trainer — they look and work very differently.
Do I need a flight simulator installed?
No. This is a browser-based trainer. It runs standalone and never connects to MSFS, X-Plane, or any installed software. You practise the CDU workflow, then apply what you learned inside your simulator of choice.
Is this compatible with the PMDG 737?
The field layout, page structure, and workflow match the PMDG 737 CDU closely enough that scenario practice transfers directly. Small vendor-specific details (soft-key positions, ACARS pages) differ between the PMDG, iFly, and default-sim 737 add-ons.
What is the CDU used for?
The CDU is the pilot's interface to the Flight Management Computer (FMC). Pilots use it to enter the flight plan (route, SIDs, STARs, approaches), set performance parameters (takeoff V-speeds, cruise altitude, cost index), and review navigation data throughout the flight.
Is this trainer free?
Yes — 100% free, no sign-up required. If you want 1-on-1 help from a human instructor, SimTuts offers paid live tutoring sessions, but the trainer itself is free to use for as long as you like.
What's the difference between a CDU and an FMC?
The FMC (Flight Management Computer) is the brain — it does the calculations and stores the navigation database. The CDU is the keyboard-and-display that lets pilots talk to the FMC. On the 737, "CDU" and "FMC" are often used interchangeably, but technically they're separate units.
Want to go deeper?
This trainer covers the fundamentals of CDU programming. Take your skills further with our related guides:
- PMDG 737 cold and dark startup — full startup checklist for the PMDG add-on
- FMC programming guide — how to programme the Boeing FMC from scratch
- SimBrief to cockpit workflow — generate a flight plan and load it into the FMC
- MSFS 2024 autopilot guide — every autopilot mode explained for GA and airliners
- How to fly an ILS approach — from setup to touchdown in the PMDG 737 and Fenix A320
- Airbus A320 MCDU trainer — the same interactive scenarios on the A320's MCDU
If you learn better with a human instructor watching your screen, our flight sim tutors can walk you through CDU programming, departure procedures, and approach setup in a live one-on-one session.