"Flighty" describes a person whose behavior, ideas, or affections change quickly and without warning. Such a person is impulsive, unreliable, and does not stick to plans or commitments, so the closest meaning is indecisive and irresponsible.
Option 1, light, and options 3 and 4, which connect the word to actual flying or kite flying, all wrongly assume the word flighty relates directly to flight in the physical sense. In reality the word evolved from the idea of something moving erratically like a bird in flight, and settled into meaning a person who is fickle and changeable in temperament, not someone connected to aviation or physical lightness.
Because flighty is used to criticize unstable, unreliable behavior in a person, option 2 is the correct meaning.