The Nevada Test and Training Range (NTTR) has the largest contiguous air and ground space available for peacetime military operations in the free world. The NTTR land area includes simulated air defense systems, mock airbases, and several target ranges. The NTTR was also used for nuclear testing. Today, it is home to RED FLAG and other military exercises that include countries from around the world. The NTTR map for DCS World 2 includes Nellis AFB, Creech AFB and the infamous Groom Lake AFB (aka Area 51). This map also includes the city of Las Vegas, McCarran International Airport, and Hoover Dam.
For those that pre-purchase prior to October 1st, 2015, you will receive a 20% discount and two free Red Flag campaigns (one for the F-15C and one for the A-10C). For those that pre-purchase between October 1st and the Open Alpha release in late November, you will receive a 20% discount and one free Red Flag campaign. Both of these options also include a 20% bonus savings on future purchases at full price.
Source: The Game Website.