Something slightly amiss here.
Convairs never had a freight door so bloodstock flights not possible.
Being a 4-engined jet it could have got off, empty and min fuel, from an extremely short runway if needed. The runway requirement for this would be less than for their inbound landing.
No commercial operator would arrange a flight into an airport they could not get out of again. Sounds like a bit of an urban legend. There may have been some nonsenses in the local press.