Thus buck should stop with the airline under the doctrine of "principal and agent" under which principal carries the can for whatever its agent/contractor either does or omits to do. Most contracts for the supply of services are on the basis of 'all care and no responsibility'; I doubt that anyone doing business with Jetstar, or any otther airline for that matter, would insist on anything less. An airline can give its contractors a right bollocking when they stuff up but when its all said and done, the airline has to shoulder the responsibility for its agents activities or inactivities.
Was the Jetstar spin-doctor rattling his sabre and sending a message to its future customers that they shouln't carry gas cylinders on their aircraft??