Airbus says it has already firmed commitments for the aircraft but that its customers had preferred not to announce them until Airbus formally offers the aircraft at the end of the year.
But it seems one order has leaked. SIA has just announced that it has increased its orders for the A350 XWB with an additional 30 A350-900s, plus options for a further 20 aircraft. It's been rumoured that it has also signed as the launch customer for the A350-900 regional.
As for other buyers, our guess is as good as any, but we do know that Airbus is targeting the intra-Asian, Middle Eastern Europe and transatlantic markets.
The A350-900 regional was devised to rival Boeing's 787-10. Airbus says it will offer the same payload and range, similar economics but five or six more seats than the 787-10, with nine-abreast seating at 18in.
Airbus' regional variant is going to be structurally identical to the standard A350-900, but its Rolls-Royce Trent XWB engines will be derated to 75,000lb thrust. Its maximum take-off weight (MTOW) will be limited to 250 tonnes, which compares to 268 tons for the standard A350-900.
Operators will then be able to revert to the full 268 tonne MTOW for an additional fee.
Another difference between the 787-10 and A350-900 regional is that the latter will not operate at its maximum thrust, meaning operators can save on maintenance costs, Airbus has said.
So what does all this mean for the market? Well, it means more competition among OEMs, which means better value for the customer, but it also means that Airbus is concerned about the 787-10.
Airbus' reaction shows how confident it is in the success of the 787-10. In fact, Airbus must think that the market for the 787-10 is so vast, it wants a piece of that pie too. Considering the 787-10's success at the Paris Air Show, it's no surprise.