Cathay Pacific Airlines has confirmed its plan to replace its aging Boeing 747-400 fleet with Airbus A350-1000s in a new $4.2 billion deal signed at the Farnborough International airshow yesterday. The Hong Kong-based carrier has placed new orders for 10 aircraft, and will convert 16 existing orders for the A350-900 into the larger variant.

Acquisition of the A350-1000s is subject to the approval of the airline’s board of directors, but with chairman Christopher Pratt and chief executive John Slosar having flown all the way to the UK to participate in an Airbus press conference this would seem to be a foregone conclusion. The A350-1000s will be powered by two 97,000-pound- thrust Rolls-Royce Trent XWB engines–the most powerful ever developed for an Airbus aircraft–which would be covered by a long-term TotalCare service support contract.

The Cathay A350-1000s typically will accommodate 350 passengers in a three-class cabin configuration and are planned to be able to fly 8,400 nm nonstop. The wider A350 family, dubbed XWB for “extra wide body” by Airbus, is a new mid-size, long-range design comprising three models seating between 270 and 350 passengers and scheduled to enter service in 2014. The manufacturer claims firm orders for 548 aircraft from 34 customers.

The announcement came seven days after the airline declared in a company environmental report that it might not have found the most effective sustainability solutions. “But we are striving to find them,” it said.

A year ago, at the Paris Air Show, Airbus confirmed that, with engine supplier Rolls-Royce, it had decided to review the A350 design and performance criteria in a bid to attract customers for the largest variant. The more powerful Trent XWB extended range by an additional 600 miles but the program would run two years later than originally scheduled.

Yesterday, Airbus said it is possible that any airline wanting to fly the A350 at the original lighter -1000 specification (the manufacturer held orders for 74 of them at the time of the design review) would be able to operate at a lower gross weight with de-rated engines.

Slosar acknowledged that Cathay had “not been shy” about making its requirements known before Airbus reworked the design. It required passenger comfort, environmental efficiency and good operating economics. Airbus president and chief executive Fabrice Bregier said it is part of the manufacturer’s job to listen as had been confirmed by the “very successful” launch of the A350-900.

The Cathay official said he believes Airbus is making very good progress on development of the higher-weight A350-1000, which the airline always had in mind when choosing a new aircraft. The greater range of the latest variant would enable Cathay to operate “nonstop to anywhere in the world that we [fly to].”

But Slosar deflected questions about any aspirations to order the larger A380 quad-jet, saying that the airline’s operation of large twin-engine widebodies had been “a huge success” with four 15-hour flights a day between Hong Kong and New York. Nevertheless, one “should never say ‘never’; the efficiency of long-haul [services] is very important for ‘Hong Kong to the world’ and ‘the world to Hong Kong’ [operations].”