I guess it's possible to create a meta-installer, which fires up the individual installers using the command line. It's not the ideal way to do this, but it might work.
Sample code to use the command line from within Flex:
var file:File = File.desktopDirectory;
file = file.resolvePath("secondAirProgram.air");
var nativeProcessStartupInfo:NativeProcessStartupInfo = new NativeProcessStartupInfo();
nativeProcessStartupInfo.executable = file;
var process:NativeProcess = new NativeProcess();