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Sprint declined to comment on the results for this story, but T-Mobile said it's already making upgrades.
"T-Mobile has made significant enhancements to the network since this testing was conducted, including launching 4G LTE in 116 metro areas reaching 167 million people," Grant Castle, vice president of engineering at T-Mobile, told CNBC. "We plan to have 4G LTE coverage nationwide by the end of this year."
RootMetrics ranks the airports and services based on the speed and reliability of airport signals, average download and upload speeds, and network reliability as well as the performance of email, apps and the Web.
On an airport-by-airport basis, the testers found huge differences and variances by time of day and location. "Baggage-claim areas, down in the basements, are typically the worst," said Moore, "So if you're trying to get in touch with someone to pick you up, that can be a big challenge."
The varied results make it hard to say which airports overall are the best and worst. "We looked at both reliability and speed, since those are the two factors that mean most to consumers," Moore said.
"Across the 50 airports that we tested, Verizon was the only carrier to record a perfect score for network reliability. They did so in four different airports—Austin (AUS), Charlotte (CLT), San Antonio (SAT) and San Jose (SJC). On the flip side, Sprint's network reliability performance at George Bush Intercontinental Airport in Houston was the lowest we recorded across the 50 airports."
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