An aircraft gets in stall when it flies at critical angles of attack, at high or low speeds so that the aircraft falls to
ground like a stone. Stable aircraft are able to fly greater maneuvers at low speeds without stalling and they recover fast from stall, some examples for very stable aircraft are the F-22 Raptor due to the advanced electronics, the airframe design and the good aerodynamics, the Su-47 and the Grumman X-29 because of the forward swepted wings. One thing that is needed to boost the Stability is thrust vectoring, what leds to post-stall maneuvering.
Tailless Flying wing aircraft like the B-2 or the Horten 229 have problems with their stability and they stall fast, to prevent this an advanced fly-by-wire system is used on the B-2 and the F-117.
Trivia[]
The slowest speed a plane can fly without stalling is called Alpha Max.