flighty

adjective, flight·i·er, flight·i·est.

1. given to flights of fancy; capricious; frivolous.
2. slightly delirious; light-headed; mildly crazy.
3. irresponsible: He said I was too flighty to be a good supervisor.
4. Archaic. swift or fleet.

adjective flightier or flightiest

1. frivolous and irresponsible; capricious; volatile
2. mentally erratic, unstable, or wandering
3. flirtatious; coquettish