Hong Kong Airlines' tentative order for the Airbus A350 XWB will involve converting 15 of its current backlog of 23 A330s.
Airbus has clarified the details of the memorandum of understanding disclosed during the Farnborough Air Show.
HK Airlines' backlog comprises 22 A330-200s and a single A330-300, plus 30 A320s.
But the new memorandum, if firmed, will increase the A330-200 total by 10, and convert 15 of the previous A330s to A350s.
This will bring its overall long-haul orders to 15 A350s and 18 A330s.
HK Airlines president Yang Jian Hong says the A350 will "become our new flagship towards the end of this decade".