Thats called 'Instant Action' and is common in every PC flight sim.
You usually always start in the air with the enemy within attacking distance or very close to.
I think if they made a demo where you had to fly for 10-20 minutes just to attack most people would put the game off as boring.
Mind you thats just for the demo and the full game will have take offs/landing as well as longer missions with better objetives.
Just think of the demo as a deathmatch map