This is an old advertisement.

It is advertising the DC3 cargo service which was offered by Air Niugini.
Thanks to Michael Pearson for the advert

The advert reads:-

WHO NEEDS TRAINS WHEN WE'VE GOT PLANES

Air Niugini has a new deal for cargo services in Papua New Guinea. We've stoked up our reliable DC3 aircraft to run scheduled freighter services. We call them "SKYTRAINS". We're offering advance reservations, quantity discounts and air express. Let us shunt your cargo quickly around Papua New Guinea on our railroad in the sky. Find out the full details by 'phoning Air Niugini's Cargo Department in Port Moresby.

It then goes on to give a few phone numbers which are no longer in use. Needless to say that the DC3's are no longer in use as well :-)