Two boys flip in the air.
The boys are on a field.
Flip in the air is not necessarily on a field.
exists e1 x1 x2.(n_air(x2) & in(e1,x2) & Actor(e1,x1) & v_flip(e1) & n_boy(x1) & card_eq_2(x1))
exists p1 x1.(n_boy(x1) & exists x2.(on(x1,x2) & n_field(x2)))