Passenger jet sales will reach $4 trillion over the next 20 years, Boeing predicted on Thursday as it hiked demand forecasts on the eve of the Paris Air Show.

The U.S. planemaker estimated a total of 33,500 jetliner sales by all manufacturers between 2011 and 2030, led by Asia which has already toppled North America as the busiest region for air travel and is set to dominate coming decades.

Last year Boeing predicted 30,900 plane sales worth $3.6 trillion over 20 years up to 2029.

The increase partly reflects a healthier starting point as the aviation industry has already turned the corner from recession. But it also factors in an 8 percent increase in anticipated demand for single-aisle jets like the Boeing 737 and Airbus A320, a segment of the market worth $2 trillion.

The world market has recovered and is now expanding at a significant rate, said RandyTinseth, vice president of marketing at Boeing's commercial division.

Boeing's forecast includes 11,450 new passenger jets for Asia in a confirmation of the region's transport-intensive growth despite the expansion of high-speed rail networks in China.

The core of the aviation market has now moved from the U.S. and North America to the Asian-Pacific market place, Tinseth told a news conference.

By the end of 2012, there will be 12,000 km of high-speed rail lines in China, as much as in the rest of the world.

That will curb some demand for air travel but will also promote economic growth that should result in further investment in air travel, with 97 airports set to open in China by 2020, Tinseth said.

Boeing and European rival Airbus face new competition from countries like China and Canada for sales of single-aisle passenger jets in the 150-seat category, the backbone for many fast-growing low-cost airlines.

Sales of a revamped Airbus A320 passenger jet are expected to dominate the Paris Air Show, but Tinseth reiterated that Boeing had not yet decided whether to do its own upgrade.

(Reporting by Tim Hepher; Editing by James Regan)

(This story corrects billion to trillion in paragraph 3)

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