[godzyla]

Jet engines wont restart in the air and dont start when youre not on an airfield.

Wrong, the Me-262.
You can restart the engines with a minimum speed of 350 kph and a height below 3,000 meters.
But before restarting the engines, set throttle on 25-30% for the engine you want to restart, it's very important because if you set it at 0%, when you'll increase throttle (little by little) the engine could be on fire (90-95% of cases).