To me this is way more readable:

    SELECT 
        t.passenger_name, 
        t.ticket_no, 
        bp.seat_no
    FROM 
        Flights f, 
        Ticket_flights tf, 
        Tickets t, 
        Boarding_passes bp
    WHERE 
        f.flight_id = tf.flight_id 
        AND f.arrival_airport = 'OVB'
        AND tf.ticket_no = t.ticket_no
        AND t.ticket_no = bp.ticket_no
        AND tf.flight_id = bp.flight_id;