2015 passenger levels at Sea-Tac through September topped 32 million, up 13.3 percent from the previous year. That includes fast-growing international travel, up 15.2 percent year to date.

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After a summer of record-breaking monthly passenger traffic, the number of passengers to pass through Seattle-Tacoma International Airport cooled in September, but the airport is still on track to set a passenger record for the fifth straight year.

The Port of Seattle released airport passenger numbers Thursday, reporting almost 3.7 million passengers for September, up almost 13.6 percent from the same period a year ago.

Sea-Tac is considered the fastest-growing of the top 20 airports in the U.S., according to a report published by OAG, formerly Official Airline Guide. And last year’s passenger count put the airport at 13th busiest in the nation.

In June, Sea-Tac surpassed 4 million passengers in one month for the first time. That record was then bested in July, and again in August, which hit almost 4.5 million passengers.

Overall, 2015 passenger levels through September is just over 32 million, up 13.3 percent from the previous year. That includes fast-growing international travel, up 15.2 percent year to date.

“We have already surpassed the numbers for the entire year of 2007 — that’s how fast this region is growing,” Port of Seattle CEO Ted Fick said in a release.

The Port projects passenger traffic reaching 66 million by 2034, according to the release. To accommodate the growth, the Port has budgeted $1.9 billion for projects over the next five years, including the renovation and expansion of the north satellite, a new international arrivals facility, a new high-speed baggage system and reconstruction of the center runway.