Tempo defines the rate at which air operations are performed. These variables directly impact how quickly your aircraft may return to operations. Sustained operations have a longer turnaround time. While Surge operations offer a potential for shorter rates initially but the maintenance must still be performed and, if flight hours are exceeded, will need to stand down. You must set Surge or Sustained via the Doctrine menu, define which type of aircraft uses it, and also enable it via the Air Operations - F6
Sustained ops are long term, sustainable operations that can continue indefinitely. You may use a single quick turnaround.
Surge ops allow for the maximum Quick Turnarounds, however this is only if your flight time for that aircraft is not exceeded.
A unit without the ability to perform a Quick Turnaround will require the surge time as listed on the loadout in order to launch another sortie.
When active the aircraft will land, refuel and rearm, and take off again. A certain amount of accumulated flight hours will determine if you can continue this operation. Only certain weapons loadouts are able to quick turnaround. Of note, you may swap between loadouts as long as they are also quick turnaround. For example you can start with iron bombs, switch to rockets, and end with anti-ship missiles.
Once you have met flight time, regardless of combat or weapons usage, the units must stand down for the loadout time.
Forces may use quick turnaround as they have the doctrinal training to allow for it. Swedish, US, and Israeli units typically have many QT options. Other nations may be limited to certain specific loadouts.
The above SU-27's may only quick turnaround with A/A loadouts.