South African cities are generally far apart. In the 1970s Jo'burg to Cape Town was a 1200 mile drive on poor roads with a maximum speed limit of 50mph**; a very slow train; or a 45 minute plane flight.
A computer centre in Cape Town had somehow managed to wreck all the copies of its 8mbyte system disk***. This was an emergency. It was decided that the fastest way to send a regenerated replacement from Jo'burg was by air. To avoid the problems of the notoriously rough baggage handlers it was arranged for it to be handed to the next passenger plane's pilot.
Things became tense when the computer centre complained about not receiving the new disk when expected. It eventually transpired that the pilot had forgotten about the disk. It was still sitting in the aircraft - which was now back on the tarmac in Jo'burg.
**A 16 year old boy once claimed to have made the trip by car in 12 hours - having gone past several towns' speed patrols before they could react.
***In those days an 8mbyte disk pack was a sizeable object (50cm x 15cm??) - and fragile.