Airbus predicted that the airline industry will need to spend $4.6 trillion on some 31,000 new aircraft over the next 20 years in its latest market forecast, released Wednesday.

From 2014 to 2033 passenger traffic will grow at an annual rate of 4.7 percent, requiring more than a two-fold increase in today’s 18,500-strong passenger fleet of airplanes carrying more than 100 seats, it said. At the same time, operators will retire some 12,400 passenger and freighter airplanes, according to the report.    

Economic growth rates in emerging markets such as Asia, Latin America, Africa and the Middle East continue to outstrip more economically developed regions. Demographic forecasts suggest that the middle classes in Asia will quadruple in size by 2033, while, globally, they increase from 33 percent to 63 percent of the world’s population. As a result of increased urbanization and concentration of wealth, the number of what Airbus terms aviation mega-cities will double to 91. Business and individuals in such cities will create 35 percent of the world’s GDP, said Airbus, and 95 percent of all long-haul traffic will go to, from or through them.

In advanced economies, international traffic flows will grow the fastest, while in the emerging economies of Latin America, Africa and Asia Pacific intra-regional and domestic flows will grow faster, said the report. For example, stimulation of new traffic coupled with increased accessibility of air travel will see India record the fastest growing domestic flows, becoming one of the 10 largest markets by 2033.

In the widebody market, Airbus sees a continuing trend toward larger models. The company forecast a requirement for nearly 9,300 widebody passenger and freighter aircraft over the next 20 years, valued at some $2.5 trillion. The estimate accounts for 30 percent of all new aircraft deliveries over the forecast period and 55 percent by value.

“We see especially strong growth in widebody twins such as our A350 XWB and A330neo. Demand exceeds supply for these new generation aircraft, especially in the 2017 to 2022 time period and beyond, so naturally we are studying production increases on both models,” said Airbus COO for customers John Leahy.

Widebody demand will include some 7,800 twin-aisle aircraft carrying between 250 and 400 seats and some 1,500 so-called very large aircraft with more than 400 seats for operation on the busiest routes, according to Airbus. Reflecting a higher than average growth and concentration of populations around cities, manufacturers will deliver almost half of the new passenger widebodies to carriers based in the Asia-Pacific region, followed by the Middle East (16 percent), Europe (15 percent) and North America (9 percent).

In the single-aisle market, Airbus sees a requirement for more than 22,000 new aircraft worth $2.1 trillion over the next 20 years, an increase of 2,000 aircraft compared with the company’s previous forecast. Those aircraft will account for 70 percent of all new units sold and 45 percent of the value of all deliveries, said the company.

Demand for single aisle-aircraft will remain high in markets such as Europe and North America, where airframers will deliver some 22 percent and 21 percent of single-aisle aircraft, respectively, according to the forecast. However, Airbus predicts that Asian demand will overtake both regions, driven primarily by the domestic markets in China and India, as well as the growing low-fare segment in Southeast Asia. The report predicts that some 37 percent of all new single-aisle airplanes will go to the Asia-Pacific region.