Boeing expects to continue building the world’s most popular jetliner, the 737, into the 2020s in Renton, a top Boeing official said in an economic speech Tuesday.

That’s good news, especially with Wednesday’s news that Boeing is going to open a second production line for the 787 Dreamliner in South Carolina, rather than expand production in Everett.

Mike Bair, vice president of Business Strategy and Marketing for Boeing Commercial Airplanes, gave the keynote address at the annual Renton Chamber of Commerce Economic Forecast Luncheon.

What’s significant about comments from Bair is the timing of when Boeing would consider launching a replacement for the 737.

Alex Pietsch, the city’s administrator for the Department of Community and Economic Development, said after the speech the word from Boeing has been a 737 replacement could come on line sooner.

The concern is whether the 737’s replacement would be produced in Renton, where Boeing has a workforce of about 9,000 employees.

Overall, Bair’s message was “positive,” said Pietsch.

Part of the reason for a longer production life for the 737 is that what makes the 787 a popular aircraft doesn’t “scale down” well into smaller airplanes, Bair said.

The 787 relies heavily on “composite” materials, Bair said. He noted that Boeing is running out of ways to use aluminum.

There’s also almost “zero” chance that Boeing would move an entire production plant, Bair said to applause. He pointed out that after making about 6,000 737s, Boeing is “really good at it.”

So despite a hopeful message about Renton, Bair spoke about how the global economy is affecting Boeing’s fortunes, and not to the good. Still, he sees a “glimmer of hope.”

Despite the fact the recession has severely reduced the airlines’ appetite for new airplanes, the “fundamental demand” for air travel will remain, Bair said.

Low-cost airlines are on the rise, and they almost exclusively use single-aisle airplanes, such as the 737, he said.

“That’s good for Renton,” Bair said.

Also good for Renton and other production plants is the massive order backlog for Boeing jetliners, estimated at about $254 billion in the third quarter of 2009. The backlog has helped stabilize the company’s production rates and maintain a relatively stable workforce.

The 737 is sold out to the end of 2015, Bair said. Production at the 737 plant is running at its highest rate ever.

Bair called the Renton plant a “lean enterprise,” indicating Boeing plans to transfer the lessons learned to lean out the 737 production to Everett.