* Leaves over a third of 2012 delivery forecast for Q4
* Canceled private jet and commercial aircraft orders weigh
* Undermines expectations for financial results due Oct. 23
* Backlog down to $12.4 bln on cancellations, weak demand
By Brad Haynes
SAO PAULO, Oct 10 (Reuters) - Brazil's Embraer, the world's largest maker of regional jets, said on Wednesday that deliveries of commercial and executive jets fell in the third quarter, making it harder for the company to meet its annual targets this year.
The planemaker delivered 40 civil aircraft from July to September, down from 55 jets in the previous three months and 46 jets in the third quarter of 2011.
Embraer forecast between 195 and 215 deliveries of commercial and executive jets this year, but has delivered just 129 in the first nine months. The manufacturer does not announce deliveries of military aircraft.
The weak deliveries cast doubt on some analysts' upbeat outlook for Embraer's quarterly financial results due Oct. 23, raising the possibility that the company could miss annual targets for revenue and profit margins.
Bank of America Merrill Lynch analysts led by Ronald Epstein told clients in a note last week that they expected deliveries of 62 commercial and executive jets in the third quarter.
Even with fewer regional jet deliveries in the quarter, Embraer was unable to meet its target of booking a new order for every commercial airplane delivered. The company booked a net five new regional jet orders, compared with 27 deliveries.
With that, Embraer's backlog of firm orders, which is its pipeline of future revenue, fell to $12.4 billion at the end of September -- its lowest in more than six years -- down from $12.9 billion in June and $16 billion a year earlier.
Embraer's executive jet division has especially lagged behind its targets this year, with 46 deliveries in nine months, compared with a full-year forecast of 90 to 105 jets. The company has struggled with canceled private jet orders, Chief Executive Frederico Curado said last month.
Curado said the business jet market will take a few more years to return to its 2007-2008 heyday for Embraer. The head of the executive aviation unit said in an August interview that global demand for his portfolio remained flat, in contrast with growing confidence from rivals like Cessna, owned by Textron Inc .
Embraer has also seen orders deferred by some customers in Europe, a senior executive said in June, and the ongoing debt crisis has since led to cancellations.
Italian airline Alitalia cut its outstanding orders for Embraer's E-175 regional jets from six in June to two in September, according to the backlog released on Wednesday.
Embraer delivered 27 commercial jets and 13 executive jets from July to September this year, compared with 28 commercial planes and 18 executive aircraft in the third quarter of 2011.
The company also lagged well behind its delivery target late last year because of an earthquake in Japan that interrupted the supply of engines with Japanese parts. Embraer eventually delivered 204 civil aircraft in 2011, missing a target of 220 deliveries that year and falling from 246 deliveries in 2010.