* Azerbaijan Airlines orders 4 new E-190s, 2 used E-170s
* 2013 deliveries help Embraer's push for stable output
SAO PAULO Nov 14 (Reuters) - Brazil's Embraer SA booked a firm order from Azerbaijan Airlines for four new E-jets, filling empty production slots and raising the chances of stable output next year from the world's largest maker of regional jets.
The order from Azerbaijan's national airline, worth $181 million at list prices, bolsters Embraer's presence in a frontier market as it faces cancellations in Europe and hopes for an order from a major U.S. airline by the end of the year.
Without new commercial jet orders by early 2013, Chief Executive Frederico Curado said last month that Embraer would not be able to maintain stable E-Jet production next year, as its order backlog hit a six-year low on vanishing demand.
Azerbaijan Airlines, which also ordered two used jets through the Embraer's ECC Leasing, will be the tenth airline flying the planemaker's E-Jets in Eastern Europe and Central Asia and the region's seventh new client since 2010.
Embraer's E-Jets have pioneered a larger regional aviation segment over the past 10 years. Its planes seat 60 to 120 passengers and are bigger than traditional regional jets and smaller than most narrowbody aircraft made by industry giants Boeing and Airbus.
Paulo Cesar de Souza e Silva, the head of Embraer's commercial aviation unit, told Reuters in September that the company's push into the region would continue in coming years.
Embraer has moved into the backyard of Russian planemaker Sukhoi, whose new regional Superjet has more than 200 firm orders but faces challenges as authorities investigate a May crash that killed 45 in Indonesia.
New frontiers are increasingly important for Embraer as demand dries up in Western Europe, where it has sold hundreds of E-Jets in the plane family's decade of service.
The planemaker booked about one new E-jet order for every three it delivered in the first nine months of the year, draining its backlog - a pipeline of future revenue - to the lowest level since 2006.
Delta Air Lines Inc is the U.S. carrier most likely to make a major regional jet order this year, Curado said on a September conference call.
Delta executives confirmed they planned to decide by the end of 2012 on bids from Embraer and Canadian rival Bombardier Inc to replace their 50-seat fleet with larger regional jets.
Azerbaijan Airlines will begin receiving its two used E-170 jets in the second quarter of 2013 and its four new E-190 jets in the following quarter. All the aircraft will be in service by the end of next year.