The A350-1000 has an 11-frame stretch over the -900 and will enter service after the -800. It is the largest variant of the A350 family and will seat 350 passengers in a 3-class cabin 9-abreast layout. It will have range of 15,600 km (8,400 nmi). It is designed to compete with the Boeing 777-300ER and replace the Airbus A340-600.

The A350-1000 will feature a slightly larger wing than the -800/900 models; a trailing-edge extension increasing its area by 4%. This will extend the high-lift devices and the ailerons, making the chord bigger by around 400 mm, optimising flap lift performance as well as cruise performance.