Thai Airways announced Monday that it would acquire 23 Airbus and 14 Boeing airplanes for about $3.9 billion to modernise its ageing fleet after a period of financial turbulence.

The carrier said the deals, which have been approved by its board of directors, would enable it to grow profits and be among the top three leading airlines in Asia in terms of quality and service efficiency.

The airline plans to buy six Boeing 777-300ER planes, four Airbus A350-900s and five A320-200s for a total of about $1.6 billion, for delivery between 2014 and 2017.

It will also lease 22 aircraft, including eight Boeing 787 Dreamliners, to be delivered between 2012 and 2017, a company statement said.

"Acquiring new aircraft made from lightweight and non-corrosive composite material to replace retiring aircraft will save fuel and maintenance costs," it added.

The company is bouncing back after a tough spell that saw it sink 21.3 billion baht ($702 million) in the red in 2008 owing to the global financial crisis, high fuel costs and political protests that temporarily shut Bangkok's airports.

The carrier posted a net profit of 1.6 billion baht in 2010, up more than threefold compared with 2009 as revenue more than doubled.

The airline faces increased competition from regional low-cost carriers such as Air Asia and last year announced plans to start its own budget airline in cooperation with Singapore's Tiger Airways.

Currently Thai Airways operates a mixed fleet, including some ageing Boeing 747 jumbos and Airbus A300s, which are no longer being produced.

Thai Airways president Piyasvasti Amranand admitted in October that the carrier's planes were "pretty old" and said the company needed to move quickly given the backlog of orders facing Boeing and Airbus.

The new orders are on top of a plan announced a year ago to take delivery of seven Airbus A330-300s medium-range aircraft and eight Boeing 777-300ER long-range planes by 2014 on lease.

The group has delayed delivery of six Airbus A380s, now due to arrive starting from 2012, because of a shortage of cash.

The launch of Boeing's new 787 Dreamliner, heralded as a new generation of highly fuel-efficient mid-sized aircraft, has been repeatedly delayed due to a string of technical mishaps.

Delivery of the first 787s is now scheduled for the third quarter of 2011 to inaugural customer All Nippon Airways of Japan.