FsPassengersP3D for Prepar3D 4.0.0.0 was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this software available.
According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software. The program lies within Games, more precisely Simulation. This tool was originally designed by SecondReality Software s.a.r.l. The following version: 4.0 is the most frequently downloaded one by the program users.
From the developer:
FSPassengers adds a lot of realism to the world of Flight Simulators. The program adds passengers to your flights, keeps detailed logs and statistics for every flight, provides in-flight passenger services such as movies, music, and drinks, and more. Also, it includes more than 1200 in-flight sounds to immerse you in the ambiance of flight. This version is designed for Prepar3D v2 and v3.
You may want to check out more software, such as FSX to Prepar3D Migration Tool, OpusFSX for FSX and Prepar3D Flight Simulators or Washington National Airport - FSX-Prepar3d, which might be similar to FsPassengersP3D for Prepar3D.