Boeing and Turkish Airlines have finalised a firm order for 15 777-300ER airplanes worth $4.7 billion at list prices.

The agreement, first announced in October as a commitment, also includes options for five additional 777-300ERs and is the largest order by value in Turkish Airlines’ history.

Turkish Airlines’ fleet currently includes 12 777-300ERs, the first of which Boeing delivered in October 2010.

Over the past two years, these airplanes have formed the backbone of Turkish Airlines’ long-haul operations.

This latest order will enable the Turkish flag-carrier to continue to serve new destinations worldwide.

“This latest order from Turkish Airlines is testament to the key role the 777 has played in the carrier’s long-haul route expansion,” said Todd Nelp, vice president of European sales, Boeing Commercial Airplanes.

“In recent years, Turkish Airlines has been incredibly successful in providing its passengers with outstanding service to a growing range of international destinations.

“The exceptional performance of the 777-300ER, with its excellent fuel economics, reliability and passenger comfort, has been a cornerstone for Turkish Airlines’ continued growth.”

The 777-300ER seats up to 386 passengers in a three-class configuration and has a maximum range of 7,930 nautical miles (14,685 km).

Turkish Airlines currently operates a fleet that includes nearly 100 Boeing airplanes and serves more than 200 destinations across 90 countries worldwide.