Seattle-Tacoma International Airport saw a nearly 13 percent increase in passenger traffic in 2015, with a record 42.3 million people passing through.

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Seattle-Tacoma International Airport saw a nearly 13 percent increase in passenger traffic in 2015, the Port of Seattle reported Friday.

A record 42.3 million people passed through last year, up from 37.5 million a year earlier. That’s an average of more than 115,000 travelers per day – nearly the population of the city of Bellevue.

Putting it another way, the Port said that in 2015 the airport had roughly the same number of visitors as Las Vegas.

The figures may not shock travelers who routinely endure long lines and delays as the airport’s aging infrastructure bursts at the seams.

Sea-Tac has been the fastest-growing large airport in the U.S. for the past two years and when final statistics are in for other airports in 2015, it’s expected to remain at or near the top in growth.

“This growth rate is nearly double what we saw in 2014 – 7.7 percent – and continues to reflect the importance of air travel and cargo to our region’s economy,” said Port Commissioner Tom Albro.

Noting that the increased air traffic creates more local jobs, he added that it also “highlights the urgency in planning for expanded facilities to meet this growing demand.”

The Port plans to build a new International Arrivals Facility for 2019 and will also renovate the north satellite terminal and install a new baggage system.

On the drawing board for later are preliminary plans for 35 more airplane gates added to the airport’s 81 current gates, and potentially an additional new passenger terminal.

In 2015, domestic passenger traffic rose 12.7 percent and international traffic 14.6 percent compared to 2014.

Air cargo numbers also grew in 2015, led by a 7.1 percent jump in international freight that followed a $20 million investment in two major air cargo projects opened in 2015 to attract the newest, larger freighters.

Sea-Tac for the first time saw more than 1,000 landings of the largest freighters in one year, including at least 175 of the newest Boeing 747-8Fs and 20 of the giant Russian Antonov-124s.