British Airways and Iberia, the two leading IAG member carriers, have joined the European Low Fares Airline Association (ELFAA).
The development is surprising because all the trade body's other participants are budget airlines such as IAG's Vueling and Easyjet, Ryanair and Wizzair.
BA and Iberia, later to be followed by Air Berlin, recently announced they were quitting the Association of European Airlines (AEA), the European trade body for conventional airlines such as Air France, KLM, Lufthansa, Swiss and so on.
The three airlines left AEA because they disagreed with how it views the Gulf carriers.
IAG CEO Willie Walsh said in a statement: "We look forward to working with ELFAA and its member airlines on a full range of policy and regulatory issues including the pursuit of further aviation liberalisation."
Membership of ELFAA would suggest that some conventional carriers have now accepted the change which is occurring in European aviation.
But, on the other hand, it's difficult to see the likes of Air France, Lufthansa or Swiss following suit.
It's too early to say what the move will mean for passengers. One would imagine that BA, for its short-haul economy class flights, could go further down the ancillary route in times to come. And that may not resonate well with some of the carrier's existing passengers.
Aviation consultant John Strickland said: "IAG's departure from AEA, its alignment with the Gulf carriers and now [its alignment] with low-cost carriers through ELFAA shows it to be a 21st century thought leader."