SINGAPORE (Reuters) - Singapore Airlines (>> Singapore Airlines Ltd.) has begun weighing a potential order for dozens of wide-body jets as it compares Boeing's revamped 777X against Europe's Airbus (>> AIRBUS GROUP) A350, three sources familiar with the matter said.

The airline is looking at a potential order for as many as 40 777X aircraft in a deal potentially worth $15 billion at list prices, the sources said, asking not to be identified.

However, a decision is not imminent since the airline is keen to closely study the Boeing 777-9X's economics. No announcements are expected at this week's Singapore Airshow.

"We discuss fleet requirements with manufacturers on a regular basis in line with our longstanding policy to maintain a young and modern fleet," a spokesman for the airline said by email.

"Any discussions with manufacturers are kept confidential, however."

Asked about interest in the Boeing 777X, Chief Executive Goh Choon Phong told Reuters the airline was gathering information on the aircraft as a potential future replacement for its existing 777 fleet.

He declined to discuss further details or to confirm whether it was actively involved in talks.

"When there is something to announce we will do so. We do not confirm our (purchasing) campaigns until there is a decision," he said on the sidelines of a conference.

The 777X was launched with record orders at the Dubai Airshow in November. The largest of two variants, the 777-9X, will carry 406 passengers and enter service in 2020.

Boeing launched the latest version of its most profitable plane in an attempt to leapfrog Airbus's 350-seat A350-1000.

A major customer of both jetmakers, Singapore Airlines has firm orders for 70 Airbus A350s and options for another 20.

It can convert some of those to the A350-1000 variant for long-haul requirements and is seen as certain to receive counter-bids from Airbus to avoid or blunt any Boeing order.

Airbus and Boeing both declined to comment.

(Reporting by Siva Govindasamy and Tim Hepher; Editing by Jeremy Laurence)

Stocks treated in this article : AIRBUS GROUP, The Boeing Company, Singapore Airlines Ltd.