Codesharing is a way of airlines selling each other's tickets and then sharing passengers on a flight offered by the partner airline, while interlining involves partner airlines operating one connection on a two-leg journey.
"Is it possible that eventually we look at the possibility of commonality of their network with our own network? I would lie to you if I said we didn't look at that possibility. Is it going to happen? I don't know," Jean-Francois Lemay, President-General Manager of Air Transat said in an interview.
He said talks were at an early stage and the pair were not on the verge of concluding any agreement. Thomas Cook declined to comment.
Air Transat, part of Canadian tourism company Transat A.T. Inc, and Thomas Cook Airlines are in the first year of a seven-year deal to exchange aircraft on a seasonal basis.
This winter, Air Transat will fly ten of Thomas Cook's A321 short-haul planes between Canadian and Caribbean destinations, while Thomas Cook will use four of Air Transat's larger A330s to fly Europeans to long-haul destinations, such as the Caribbean.
In the summer months, the planes return to their owners for use on each company's main routes.
For Air Transat, that's carrying tourists from Canada to Europe and vice-versa, and for Thomas Cook, that's using the short-haul A321s to fly customers on holiday packages between northern Europe and the Mediterranean.
Lemay said Thomas Cook was a good partner and the pair were having frequent discussions, which had evolved into talks about networks and the potential for a deepening partnership.
(Reporting by Sarah Young; Editing by Mark Potter)