Would it be possible to enable the option of ordering a new aircraft with a hush kit fitted from the manufacturer? In cases where i.e. the DC-9 still is in production when noise regulations are coming into force, it would be a "nice-to-have" if an order for new DC-9s with a hush kit fitted before delivery could be placed. That would mean a simpler process in upgrading a fleet of aircraft still very much usable, but lacking in the noise department, with newer airframes certified for Chapter 3 noise regulations without having the hassle of fitting hush kits after delivery. The cost for the upgrade could be added to the purchasing cost (or lease cost if applicable).