phpVMS is the most popular, free, virtual airline software, with support for various ACARS applications (kACARS, FSACARS, XAcars, FS Flight Keeper, and FSPassengers), AJAX-driven administration panel, complete with financial reports, schedule management and various other features designed for realistic operation of your virtual airline.
phpVMS was started back in March 2008 by Nabeel Shahzad, when there was no real virtual airline management system available to use. Since then, it's grown to be the top VA management tool, supporting various ACARS applications, and a lively community. phpVMS is written on solid design principles, making it easy to modify and extend, with little effort. It's written in the MVC (Model-View-Controller) pattern, allowing you to easily customize the entire look and feel, by just manipulating HTML and CSS. READ MORE
Even though phpVMS is free, there are still many costs, including server and hosting costs for new and upcoming features. Any amount will be greatly appreciated!