A jet from the Chicago Air & Water Show took a little detour from its route to fly over Wrigley Field on Friday ... scaring the crap outta Cubs players -- and interrupting Hayden Christensen's "Take Me Out to the Ballgame" rendition too!
The wild moment went down during the seventh inning of Chicago's tilt with the Pirates, just as Christensen and his daughter were gearing up to serenade the stadium.
They began singing into mics .