The Liberal Party has reaffirmed its vow to keep jets out of Billy Bishop airport by refusing to reopen the agreement that spells out what types of planes can, and can't, fly out of the Toronto Islands.

A source close to prime minister-designate Justin Trudeau said Monday the party stands by its refusal to amend the tripartite agreement, which would shoot down Porter Airlines CEO Robert DeLuce's campaign to fly passenger jets out of an expanded island airport.

Nine Toronto Liberal MPs — including Adam Vaughan, Carolyn Bennett and Chrystia Freeland — informed city council of the party's position in a June 4 letter, which also expressed support for the plan to tear down the Gardiner Expressway. 

"The Liberal Party's policies on the waterfront are as clear as they are forward looking," the letter said. 

Vaughan made similar remarks about the airport in a September letter to the anti-jet group CommunityAIR and at his election night victory party.

But the Liberals had been silent since Coun. Jim Karygiannis sent an open letter to Trudeau on Oct. 22, claiming the airport issue wasn't mentioned in the party's election platform. 

The tripartite agreement between Ottawa, the Toronto Port Authority — now called PortsToronto — and the City of Toronto governs what sort of aircraft can fly out of Billy Bishop. 

Since 2013, Porter Airlines has lobbied Toronto city council, wanting to extend the runway at Billy Bishop to accommodate Bombardier CS-100 jets, which would allow the airline to reach more destinations. 

Both PortsToronto and City of Toronto staff have been studying the idea.

Outgoing Prime Minister Stephen Harper has been a prominent backer of the plan.

At city hall, however, the proposal has been bogged down.

A refusal by the federal government to reopen the agreement would effectively kill the plan.