An air service operator shall not operate an aeroplane with an approved passenger seating configuration of more than 30 seats over routes on which the aeroplane may be over water and at more than a distance corresponding to 120 minutes at cruising speed or 400 nm, whichever is the lesser, away from land suitable for making an emergency landing, unless such aeroplane has been certified as having adequate characteristics for ditching or has been approved as adequate for ditching.