Cathay Pacific is converting six of its Airbus A350-1000s to the smaller -900, and deferring delivery of five other -1000s by a year.
The airline confirmed the shift in its orders for the Rolls-Royce Trent XWB-powered twinjets as it formally signed for a batch of A321neos.
Cathay had orders for 46 A350s including 26 of the larger A350-1000.
It had notably been the first carrier to commit to the revamped -1000 following Airbus's decision to redesign the type in 2011.
Cathay's commitment, unveiled in 2012, involved converting 16 of its -900s to the new -1000 and adding an incremental order for 10 more, giving it 26 in total.
But the latest switch will convert six -1000s back to the -900, the second such high-profile conversion in a matter of days, following United Airlines' decision to swap its 35 -1000s for the smaller variant.
Cathay's six extra -900s will be delivered in 2019-20. The carrier will defer deliveries of five of its remaining -1000s from 2020 to 2021.
Airbus points out that Cathay's order "remains unchanged" in terms of the number of A350s the Hong Kong-based airline is taking.
It had taken orders for 212 A350-1000s by the end of August this year, but the United and Cathay changes will reduce this figure to 171.
Qatar Airways remains the largest customer for the -1000, with 37 on order, while the conversions by Cathay and United mean Etihad Airways becomes the second-largest with 22.