WASHINGTON — A weaker global economy — and a slowdown in China — will likely dampen some of the growth in air travel over the next two decades.

The International Air Transport Association says the number of airline passengers is expected to double to 7 billion by 2034. That figure marks a decrease from a prior forecast of passengers totalling 7.4 billion in 2034, reflecting lower economic growth in China that will likely reduce demand for travel and potentially limit airplane orders for manufacturers Boeing and Airbus.

Despite the lower forecast, China is expected to add 758 million new passengers for a total of 1.2 billion flyers. Those gains would likely mean that China surpasses the United States as the world’s largest passenger market by 2029.