DCS is the best combat flight sim available.
You will not be able to activate these on the steam version of the game. You need to download the non-steam DCS world (for free).
Prices are USD:
DCS: F-86F Sabre: $49.99 to $14.99 (70% off)
DCS: Fw 190 D-9 Dora: $49.99 to $14.99 (70% off)
DCS: UH-1H Huey: $49.99 to $14.99 (70% off)
DCS: Mi-8MTV2 Magnificent Eight: 49.99 to $14.99 (70% off)
DCS: Flaming Cliffs 3: $39.99 to $11.99 (70% off)
DCS: A-10C Warthog: $39.99 to $11.99 (70% off)
DCS: Black Shark 2: $39.99 to $11.99 (70% off)
DCS: P-51D Mustang: $29.99 to $8.99 (70% off)
DCS: Combined Arms: $19.99 to $5.99 (70% off)
F-15C for DCS World: $9.99 to $2.99 (70% off)
A-10A for DCS World: $9.99 to $2.99 (70% off)
Su-25 for DCS World: $9.99 to $2.99 (70% off)
Su-27 for DCS World: $9.99 to $2.99 (70% off)
DCS: MiG-21Bis: $49.99 to $24.99 (50% off)
DCS: Bf 109 K-4: $49.99 to $39.99 (20% off)
That's a really good price for Flaming Cliffs 3. I have already invested in the Steam version though.