Singapore Airlines is Airbus's biggest customer for the A350-900, having placed its first order for the aircraft in July 2006.
It now has 67 A350s on firm order, including seven of an ultra-long-range model that will be delivered in 2018 for use on non-stop services between Singapore and the U.S.
Singapore Airlines expects to take delivery of 11 A350-900s in the aircraft's first year of operation and has the option to purchase 20 additional A350s.
AirAsia X, Air China, Asiana Airlines, Japan Airlines, Thai Airways and Vietnam Airlines have also placed orders for the aircraft, while Asian rival Cathay Pacific is set to receive its first A350 "in the coming months" according to reports.
"The Asian market is extremely competitive with China emerging as a big threat to traditional dominant players such as Singapore Airlines and Cathay Pacific Airways," Thomas said.
"There is also long haul competition from the Middle East giants. Plus, recently old players such as U.S.-based United Airlines are dramatically up-gauging their product with 787s and offering new non-stops such as San Francisco to Singapore from June 1."