Of course JQ will retain the revenu but if Qantas operate a Jetstar flight as a charter using Qantas flight numbers etc., then Qantas would charge Jetstar $xxxxx for the operation. Chances are that the sum of the fares collected by Jetstar would not cover the cost of the charter. This is the way in which carrier-to-carrier charters are operated. You will no doubt find an exchange of paper between JQ and QF which sets out how much JQ will pay for the charter, and who pays for what in terms of out-of-pockets such as airnav charges, handling etc etc.