Flickr.com/JasonUnbound.
Flickr.com/JasonUnbound.

If you’ve traveled through the Seattle-Tacoma International airport recently, you’ve likely experienced long lines and delays. Fortunately, mobile devices allow travelers to work, read, and otherwise make use of that dead time. But it turns out security lines aren’t the only slow-moving inconvenience at Sea-Tac.

A new report, from Bellevue-based research firm RootMetrics, lists Sea-Tac as number 31 in mobile network performance on its ranking of the 50 busiest U.S. airports. Seattle’s airport has seen an unprecedented increase in volume, trafficking 42 million passengers last year. The number of travelers grew by 7 percent in 2014 and 13 percent in 2015. The airport’s RootMetrics ranking fell from 13 in the second half of 2014 to 26 in the first half of 2015.

Big crowds don’t always correlate with poor network performance, as the RootMetric list shows. Although network congestion does occur when more people are online, several airports that handle more travelers than Sea-Tac scored higher on the list. But those airports, like Hartsfield-Jackson in Atlanta, the nation’s busiest travel hub, have the network infrastructure to handle such demands. It’s possible that providers (like airport security) were overwhelmed by the huge jump in volume at Sea-Tac over the past year.

“As you add more people, especially in as confined a space as an airport you start to really strain the capabilities of a network,” said RootMetrics VP Julie Dey. “With Seattle being, relatively speaking, a little bit more of an older airport it probably wasn’t originally provisioned to handle the kind of mobile traffic that the current passenger load is putting on the network.”

Verizon is the highest-performing mobile provider at Sea-Tac, followed by AT&T. T-Mobile, which, like RootMetrics is headquartered in Bellevue, came in at a close third in performance.

Verizon is the best-performing wireless carrier at Sea-Tac, according to RootMetrics.
Verizon is the best-performing wireless carrier at Sea-Tac, according to RootMetrics.

AT&T had the highest median download speed across all 50 airports, followed by T-Mobile. In addition to ranking the country’s 50 busiest airports, RootMetrics tested mobile data performance at the five busiest travel hubs to determine which networks performed the strongest. Verizon was the winner at four out of the five. AT&T beat out Verizon at Denver International Airport.

RootMetrics calculated airport network performance by measuring reliability, download speeds, and the number of subscribers to each of the four major carriers.

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