Military fighter jets can get in the air and to their target in minutes and faster than almost all other aircraft. How do they achieve this considering that a normal pre-flight alone takes ~10-15 minutes?
(Source - My many years on fighter jet flightlines. F-111E, F-106, F-15, F-16)
The designated jets are fully preflighted. Munitions fully loaded. INS aligned, IFF code laid in, most but not all of the safety devices removed. The jet is ready to go except for the pilot and engine start. Assigned alert pilots and ground crew are hanging around. Alert hangar right next to the runway. Can get in the air in under 5 minutes.
We had to scramble F-106 from Griffiss AFB more than once, to escort Russian Bears down the East coast.
All of the above, except the aircrew may be sitting in the seat. Rotate pilots every X hours.
Wartime or imminent threat
All of the above, but engines may be idling. All safety pins pulled.
Typically you would do a preflight like this, but it's obviously different from place to place, depending on local requirements.
Before placing the aircraft on quick response status, you would do the normal preflight procedures like inspecting the aircraft exterior, checking cockpit, following your pre-engine start check, and starting the engine.
After this, during the post engine start check, you don't remove the ground safety pins.
The aircraft is now ready for scramble, per local policies and directives - and the only thing the pilot needs is for the flight engineer to remove the safety pins.
So TLDR: They do the preflight before placing the planes on the quick response status.