In baseball, an infield fly is a fair fly ball which can be caught by an infielder with ordinary effort, which first and second, or first, second and third bases are occupied before the second out. Infield Fly Rule: On the infield fly rule the umpire is to rule whether the ball could ordinarily have been handled by an infielder not by some arbitrary limitation such as the grass, or the base lines. The umpire's judgment must govern, and the decision should be made immediately. When an infield fly rule is called, runners may advance at their own risk. If on an infield fly rule, the infielder intentionally drops a fair ball, the ball remains in play.