Boeing is exploring an ultra long-range replacement of the 777-200LR, conceptually dubbed the 777-8LX.

Likely to be the last of three members of a conceptual 777X family, the -8LX could potentially have a service entry in the 2020s, providing a mission range of 17,550km (9,480nm), industry sources tell Flightglobal, which is 85nm longer than the 17,395km (9,395nm) offered by the 777-200LR.

The reduced fuel burn per seat for the -8LX is estimated to be a 14% to 16% improvement over the 777-300ER, and the extended range may, for the first time, open the prospect of profitably operating flights between Sydney and London without a "kangaroo" stop in Southeast Asia.

Today's ultra long-range 777-200LR and the Airbus A340-500, which is no longer in production, have served in mostly niche roles for carriers requiring long-range capacity on hot and high and extended missions.

"Boeing continues to explore many options to build on the 777's popularity" including a new wing and even a clean-sheet aircraft, said the aircraft-maker, declining to discuss in detail the latest 777X concepts.

The 777-8LX's fuselage would match that of a proposed -8X, now seen as a three-class 353-seat 4.46m (14ft 7in) stretch of the 777-200ER.

With common structural elements, the -8LX and the larger -9X would share a 344t (760,000lb) maximum takeoff weight (MTOW), allowing the smaller jet to carry additional fuel for the extended missions, with a common fuel tank capacity across the conceptual family.

Both the 777-8X and -9X concepts currently aim for an 14,800km (8,000nm) design range.

With a common engine to the 777-9X, the -8LX is conceptually powered by the General Electric GE9X with a 99,500lb thrust rating, while the -8X is understood to be significantly derated off the engine's baseline design with its lower MTOW.

Currently, the 407-seat 777-9X, 2.13m (7ft) longer than the 777-300ER and, could have a service entry later this decade.

Boeing's 777X concepts have continued to evolve since the airframer formally established its advanced product development programme in January 2010, and the 777-8LX is understood to be a lower priority concept for Boeing as the heart of the market remains focused on the 777-200ER and 777-300ER-sized aircraft to respond to the A350-900 and -1000.

Early studies revolved around maintaining the 777-300ER and -200ER fuselage lengths, increasing capacity by carving out sidewalls and fuselage frames to comfortably accommodate 10-abreast economy class seating. Now Boeing's studies have expanded to bridging the product gap between a conceptual 323-seat 787-10X and 467-seat 747-8.

It is understood that part of Boeing's ongoing 777X evaluation also includes three options for a new massive carbon fibre reinforced plastic (CFRP) wing, with a potential baseline 71.1m (233ft 5in) span and raked wingtip, and 65m (213ft 3in) and 68.6m (225ft) wings with blended winglets.

The 787-inspired CFRP wing would grow the 777-300ER and 777-200LR's wing area by approximately 10%, providing slower and quieter approaches.

The 71.1m wing would push the 777 from ICAO Code E airport classification to Code F standards, the same category occupied by the 747-8 and A380. Under study is a revival of the original 777-200 wing-fold concept, which would have tilted upward a 6.9m (22ft 6in) portion of the wing that included the outer two leading edge slats and outboard aileron to accommodate McDonnell Douglas DC-10-sized gates.

Boeing's current concept scales back the weight and complexity of the design by folding only the raked wingtip, which is understood to be a 3.4m (11ft) portion of the wing, and does not house any wing control surfaces.

In short, Boeing would maintain Code E standards on the ramp and taxiway, up to 65m (213ft 4in), in line with today's 777-300ER, and shift to a Code F classification after entering the runway.

Source: Air Transport Intelligence news