Brazilian planemaker Embraer SA's backlog of firm orders rose to the highest level in almost four years in the second quarter, in a sign of rising demand for regional aircraft.

Embraer's backlog, or the pipeline of future revenue for the world's largest producer of regional planes, rose to $17.1 billion at the end of June, from $13.3 billion in March and $12.5 billion at the end of last year, the company said in a statement on Monday. It was the highest since September 2009.

During the second quarter, the company delivered 22 commercial jets, five more than in the first quarter, the statement added. Deliveries of executive jets jumped to 29 in the second quarter from 12 in the first quarter.