Malawi
Unpaid Aerogramme Endorsed "Pay Forward"

This aerogramme form was sent unstamped from NTAJA, Malawi (cds 20 Jan 1989) to Karachi, Pakistan. The sender endorsed "PAY FORWARD" in a stamps' stead.

The most likely meaning is "Pay it Forward". According to Wikipedia, "Pay it forward is asking the beneficiary of a good deed to repay it to others instead of to the original benefactor". Here, the sender asked the Post Office to pass on the aerogramme for free, which they did, though, after taxing the aerogramme "35/35" tambala, the Malawian currency.

There are no signs that the postage due was collected by the Pakistani postal authorities. So, it is still in the realm of possibility that the Pakistani postal authorities did the good deed the sender has asked for. If not, it finally was the addressee who paid the amount postage due.


Credits
Thank you, stampboard members HayeSmyth, psestamp and GlenStephens for pointing me to the concept of "Pay it forward". The stampboards thread related is here.