TransCAD

TransCAD 7 reads and writes OMX. You can open or save OMX matrices using the dialogs or GISDK. Here is a macro to save a matrix file to OMX.

Macro "ExportMatrix" (Args)

    m = OpenMatrix("E:\\autoAirportTrips_AM.mtx", )
    mc = CreateMatrixCurrency(m,"SOV_GP_AM",,,)
    CopyMatrix(mc, {
        {"File Name", "E:\\autoAirportTrips_AM.omx"},
        {"OMX", "True"}
      } 
    )

EndMacro