NEW YORK (TheStreet) -- So far, the Shanghai stock market's sharp decline hasn't scared off the airline industry, which continues to add flights rapidly and to invest heavily in China.

But it's still summer, when air traffic is high, so it can be tough to get a read on exactly what potential passengers are thinking.

Last month, Hainan Airlines launched service from Beijing to San Jose, Calif., and from Shanghai to Boston and Seattle. The flights are doing "surprisingly well," said Joel Chusid, Hainan Airlines executive director for the U.S.

"So far, we haven't seen any (decline)" due to the market downturn, Chusid said. "But ask me in November."

Hainan's growth is just a small piece of the rapid increase in airline capacity between China and North America. "The frequency of flights between the U.S. and China has more than doubled in the past five years," said Katherine Wellman, vice president of product management at aviation information company OAG.

Between 2010 and 2015, the number of airline seats between the U.S. and China grew by 119% to 7.5 million, while the number of annual frequencies grew by 133% to 25,931, according to statistics compiled for TheStreet by OAG. Throughout the period, the number of seats and frequencies operated by U.S. and Chinese carriers has been nearly equivalent.

Looking ahead, a survey released Monday by the Global Business Travel Association forecasts that China business travel will account for $420 billion in spending in 2019, up 41% from the 2014 level.

This week, two airline deals have been announced. Delta (DAL) - Get Report said it will pay $450 million to buy 3.5% of the shares of Shanghai-based China Eastern Airlines. Delta is the first U.S. carrier to invest in a Chinese airline. Additionally, Hainan and Alaska (ALK) - Get Report signed a frequent-flier partnership, linking Alaska flights with Hainan flights to Beijing and Shanghai.

"We feed Alaska a few hundred passengers a day, while Alaska feeds a similar number to Hainan," Chusid said.

"Passengers have been asking for this for a long time," he added. "It benefits both airlines."

Last week, Jim Compton, chief revenue officer for United (UAL) - Get Report , the leading U.S. airline in China, said "demand is still growing.

"We're really confident where we see demand today," Compton said, speaking on the airline's second-quarter earnings call after he was asked how to comment on China demand trends. "Although that capacity growth is strong, that demand will come in line over the next several years."

Compton said the airline industry's concern over negative passenger revenue per available seat miles throughout the world is not so important in China. "The demand side in China today actually puts less pressure on RASM than" exists in other markets where capacity is growing, he said.

As for Delta's deal with China Eastern, being the first U.S. carrier to invest in a government-owned Chinese carrier no doubt carries risk. But the potential benefit is also high.

"Our $450 million investment in China Eastern is only a part of our partnership," said Vinay Dube, Delta senior vice president for Asia Pacific, in a Delta internal publication. "While the investment results in a 3.55% stake in China Eastern and an observer seat on the China Eastern board of directors, the true value in this agreement comes from our shared vision to build a long-term, profitable partnership by creating a world-class, customer-focused offering.

"Delta has nearly tripled the size of its China network in the past five years," Dube said. "Pairing up with China Eastern increases our reach and further cements our commitment to the market and to our customers who travel between China and the U.S."

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.