When choosing an aircraft, I am unable to use the ATC call signs (United, US Air, American, etc.). I hit the drop down arrow but nothing happens. Please help me solve this. Thanks.

Download, install and run EditVoicePack.http://www.editvoicepack.com/It will add numerous airlines with their codes for MFS ATC to use.However, it's strange as you should have airlines like American, for example.Check if you have a file called airlines.cfg in your Aircraft folder.

To get the extra airline names in the drop down box from EVP, choose the Update airlines.cfg file choice in the EVP menus.Hope this helps,