Airbus would undoubtedly have preferred that two high-profile conversions away from its newest aircraft, the A350-1000, hadn't emerged within a week of one another, but the big league, with its big money, is not an arena for those short on resilience.

Taking on the Boeing 777-300ER which, for more than a decade, has held a de facto monopoly in the 350-seat twinjet sector, was never going to be a simple exercise, irrespective of Boeing's decision to pitch the 777X as a spoiler. The -300ER has the advantage of inertia combined with attractiveness of end-of-line pricing as production gradually winds down, and relatively low fuel prices means engine efficiency is less influential in building a case for shifting to an entirely new model.

Convincing United Airlines to take the A350 in the first place was a coup – the airline had previously limited its Airbus operations to the short-haul realm – and the order had appeared vulnerable given the US carrier's introduction of 777-300ERs and its requirement for a smaller type to replace the 777-200ER.

Cathay Pacific has been less partisan in its long-haul approach. Its fleet includes the 777-300ER but has opted for both the A350-1000 and 777X. In the context of an order placed five years ago, just after the -1000's controversial redesign, Cathay's conversion of a handful – which, in any case, had originally been switched upwards – is hardly earth-shaking.

In the face of a 20% cut to the -1000's order backlog, the fact that the United and Cathay rejigs nevertheless amount to a 10-aircraft gain for the A350 programme is easy to overlook. The -900 is steadily establishing a platform for which Airbus has an upgrade path, and A350 conversions have not been a one-way affair; LATAM has swapped -900 orders to the -1000 on three occasions.

Judgement of the -1000's prospects based on recent order shuffles and a dearth of sales this year would be premature. Airbus is still concentrating on delivering the first -1000 before the year is out, and an order plateau before entry into service is not unusual.

There is also a broader situation to consider: neither the 777X nor the 787-10 have achieved substantial take-up in the past two years, evidence of a weakened market for twinjets in the highest capacity sector, underlined by Airbus's backtracking on potential development of a stretched 'A350-2000' variant.

Cathay had been the first customer to demonstrate its confidence in the -1000 after its controversial 2011 revamp, Airbus having insisted that it would not redesign the aircraft a second time to appease critics.

Airbus has, at times, stumbled in making its debut on the 'big twin' battlefield. But now that the armies have met, the charge is on. Too late to turn back now.

Source: Flight International