SIA, Scoot to upgrade & expand fleet
Deliveries are due to begin in 2017, the airline said in a statement.
The airline currently operates 19 A380 superjumbos and already had firm orders in place for 20 A350s, for delivery from 2015.
SIA said the A350s are intended for use on medium and long-haul routes.
As part of the deal, SIA said Airbus will acquire its five A340-500s, which will be removed from service in the fourth quarter of 2013.
The airline said it will cease non-stop flights between Singapore and Los Angeles and between Singapore and Newark in view of a lack of replacement aircraft in its fleet with "sufficient range and operating economics".
SIA CEO Goh Choon Phong said: "Although (it is) disappointing that we will be halting these services, we remain very committed to the US market.
"Over the past two years, we have increased capacity to both Los Angeles and New York by deploying A380 superjumbos on flights via Tokyo and Frankfurt. We will also continue to explore additional options to enhance our US services,"
SIA also added that its Scoot unit will acquire 20 Boeing 787 Dreamliner aircraft to support its growth plans, in a deal worth more than US$4.0 billion at list prices.
Deliveries will start in 2014, said Scoot, which started operations in June.
The fuel-efficient new aircraft will replace Scoot's fleet of Boeing 777-200s, it added.
Scoot currently operates no-frills flights from Singapore to Sydney, Gold Coast, Bangkok, Taipei and Tianjin in China.
Services to Tokyo will start on October 29, followed by flights to the Chinese cities of Shenyang and Qingdao in November, the statement said.