Oman Air, the sultanate's national carrier, has placed firm orders for 20 737 Max single-aisle aircraft from Boeing, nearly doubling the airline's 737 fleet.

The airline's order includes conversions of six 737 NG planes to 737 Max jets, for a net gain of 14 in Boeing's order book.

Boeing and rival Airbus are battling for market share in the large single-aisle market.

Boeing had booked 2,869 orders for the 737 Max through the end of September, compared to more than 4,300 for Airbus' competing A320neo, according to the companies.

Oman Air currently operates 21 Boeing 737 aircraft, and has no Airbus A320s, according to its website.-Reuters