The wi-fi at Hartsfield-Jackson International Airport may be free, but it's not very fast, according to an analysis of wi-fi at airports across North America.

The analysis conducted by Ookla's Speedtest service, which tests Internet performance, found that Hartsfield-Jackson ranked near the bottom of a list of 30 airports across the continent.

According to Ookla, "the speeds in Toronto, Atlanta and Montréal were slower than any Wi-Fi we saw in Africa, though comparable to many airports in China."

Hartsfield-Jackson has had free wi-fi since 2014. Airport officials said then that they expected as many as 15,000 people could use the service at the same time. Throughout a single day, Hartsfield-Jackson -- the world's busiest airport -- handles an average of about 285,000 passengers.

In the Speedtest analysis released this month of data from March to May 2017, the fastest wi-fi was at Denver International Airport.

Around the country, "Free Wi-Fi is generally available, though slow in Atlanta, Minneapolis, Orlando and Phoenix," Ookla says.

"Atlanta's uploads are also snail-paced, so you probably want to wait on uploading your Walking Dead Zombie Tour pics until the next leg of your trip," according to a similar Ookla analysis in January of airport wi-fi speeds in the United States.

Hartsfield-Jackson spokesman Reese McCranie said growth in passenger volume "has outpaced our ability to keep up with increased customer demand for fast internet access. We are working quickly to fix that in the next couple of months."

He said the airport's IT team is working diligently to significantly upgrade and expand the capacity. "Our goal is to have one of the fastest, free Wi-Fi networks in the country," according to McCranie.

Cellular service at Hartsfield-Jackson fares a little better. ATL came in 19th out of 30 North American airports for cellular speed, while Vancouver International Airport was No. 1 in that ranking.

"U.S. airports are all over the map when it comes to choosing Wi-Fi or cell," according to Ookla.

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