On 26th October, 2025 AirfoilLabs shared a new development update on their forthcoming 737 MAX for X-Plane 12.
Starting off with engine tuning, the team reports they’ve made significant progress thanks to new data from real-world pilot reports. Importantly, performance as a function of Mach, altitude, and airspeed has been dialed in. Acceleration and deceleration of engine RPM have also been retuned. EEC logic and associated failure modes have been completed. Final calculations for N1-driven autothrottle modes are complete, with MCT, TO, CLB, and GA modeled in detail. Idle modes are fully functional including: ground idle, flight idle, approach idle, and so on. N2 values have also been corrected to match the real aircraft.
The flight model also received a number of improvements. Airfoils and wings have been retuned for precise performance across altitude, weight, attitude, and speed relationships in an effort to reflect the clean aircraft performance in climb, cruise, and descent. The team aims to test vertical performance with the FMS. Currently, flight model work is focused on tuning the flight spoilers, flaps, and slats to finalize takeoff, approach, and landing behavior.
AirfoilLabs is beginning to test the autopilot with the new FMS functionality. Basic modes are working, and flight behavior is satisfactory to the team. However, they indicated a lot fo work remains to implement the many interactive autopilot modes.
AirfoilLabs 737 MAX FMS Progress
Speaking of the FMS, it occupied the largest portion of the development update. Climb profiles like ECON, Max Rate, Max Angle, and RTA are computed through the VNAV CLB model. This includes acceleration segments and speed schedules from lift-off through clean-up to top-of-climb. According to the developer, this mirrors the FMC CLB logic of the real aircraft.
Acceleration handling was covered in this update. This refers to the way that speed calculations transition from takeoff/clean-up speeds to climb IAS/Mach, observe the IAS/Mach crossover, and preserve published or pilot-entered restrictions during the clean-up window. AirfoilLabs claims this modeled behavior is consistent with climb/initial-climb techniques for the 737-8.
Level-flight (cruise) stability is a work in progress. The AirfoilLabs 737 MAX calculates FMC targets for ECON/LRC/RTA cruise, including Mach/IAS propagation and step-change handling, reflecting the FMC CRZ page behavior and related options.
Route speed and vertical-limit restrictions work is also in progress. The team has implemented ALT “at”, AT-OR-ABOVE, AT-OR-BELOW, and window constraints, plus speed constraints as coded on procedures and waypoints. The system builds the vertical path to honor these limits and computes advisory deviations if a restriction is incompatible with the energy state. This tracks FMC data rules for altitude constraints, windows, and speed restrictions and constraints.
VNAV mode logic at restrictions remains a work in progress. This part of the simulation resolves VNAV path vs VNAV speed transitions, ALT INTV/speed intervention effects, and “on-approach” logic interactions described for the 737-8/-9, including updates to Altitude Intervention behavior in later FMC baselines.
The team is also working on vertical path construction. The reference path is constructed using the FMC-style method by incorporating altitude targets at constraint fixes, path segments between them, and recapture behavior. This is consistent with the FMC description of vertical path construction and descent modes.
A preview photo of the FMS and Navigation Display was included in the post and shown below.
3D Modeling and Texturing Progress
The team has been working on the glass and windows. This includes rain effects, icing effects, thermal features, and wipers. Significant time was spent correcting cockpit window meshes and creating new textures. All glass-to-frame connections are now complete. The side-panel and ceiling meshes were edited to fit the revised windows correctly. A new analog compass was created, and fuselage textures were reworked to improve the representation of bolts. New normal maps were created as part of this, and effects were added to represent dirt blown around the bolts by airflow. Several preview shots of the windows and wipers were included along with a video (all below).
No release date for the AirfoilLabs 737 MAX was provided as of the publishing of this article. To read the full development update on the AirfoilLabs Forum, click here.
