New Democrats and Liberals are both demanding an apology, but the government is fending off the attacks by saying it has slashed the use of government aircraft by cabinet ministers.
MacKay says he used the helicopter as part of a search-and-rescue exercise, but Defence Department emails suggest the pickup was explicitly set up to retrieve the minister under the "guise" of a training operation.
Opposition MPs say that's the equivalent of commandeering an ambulance or fire truck as a private taxi.
MacKay wasn't in the Commons for question period.
Government House Leader Peter Van Loan brushed off the helicopter questions, saying they have already been answered.