A group of people riding a walking belt at the airport.
The people are on the subway.
The subway is underground and not at the airport.
exists e1 x1 x2 x3 x4 x5 x6.(n_airport(x6) & a_topic(x1) & of(x1,x2) & at(e1,x6) & Theme(e1,x4) & Actor(e1,x3) & v_ride(e1) & n_belt(x4) & of(x4,x5) & n_walking(x5) & (x2 = x3) & n_people(x2) & n_group(x1))
exists p1 x1 x2.(n_subway(x2) & n_people(x1) & on(x1,x2))