Which wireless carrier has the best airport data coverage?

If you're a frequent flyer who spends a lot of time at airports in the US, you're better off using Verizon Wireless.

That's the conclusion from wireless testing firm RootMetrics, which released its bi-annual report on the state of mobile coverage in the nation's 50 busiest airport. As with the broader national test, Verizon was the winner. But when it comes to airport, the nation's largest wireless service provider was the clear winner, followed by T-Mobile, then AT&T and last-place Sprint.

It's the third consecutive time Verizon has taken the top position in RootMetrics' study, a testament to the company's focus on network performance. With the competitive landscape in wireless heating up, owning the bragging rights to the best network is a critical edge. That's particularly the case with Verizon, which has long touted the quality of its network as justification for charging a premium over more aggressive rivals.

Out of the 50 locations, Verizon took the "RootScore Award" (or tied for the lead) in 29 airports. That's actually down two airports from the study taken in the second half of 2014, but still comfortably ahead of No. 2 T-Mobile. RootMetrics praised Verizon's performance, noting that the carrier had a strong combination of speed and reliability in a majority of the airports.

T-Mobile remained in second place, but added three more airports for a total of 20 awards. AT&T likewise added three airports for a total of 13. Both networks offered similar traits of inconsistency, according to RootMetrics.

"T-Mobile's speeds were similar to what we saw with AT&T's network: good topline speed at some airports and markedly slow speeds at other airports," the report said.

Likewise, it called AT&T's performance "a mixed bag" with improved reliability.

Sprint was dead last with zero airports, losing the one award it won in the last study. RootMetrics noted that it was able to better connect to the network this time around, but that its speed consistently fell in the slower range of the competition.

"Sprint's reliability enhancements deserve praise, but the network still has room to improve when considering speed," the report said.

AT&T took the crown in the nation's busiest airport, Hartsfield-Jackson Atlanta International, not a surprise since AT&T's mobility division is based there. Verizon and AT&T tied in Dallas, which is where AT&T is headquartered.

In Verizon's backyard of New York and New Jersey, T-Mobile had the best performance at John F. Kennedy International and Newark Liberty International, while AT&T took the award for LaGuardia Airport.

Verizon, however, took the award in Seattle-Tacoma International, home to T-Mobile, and Kansas City International, Sprint's local airport.

Verizon was pleased with the results.

"We're pleased that another respected third-party organization has assessed and ranked the Verizon network highly," said a company spokewoman.

AT&T, meanwhile, noted it had enhanced coverage in 34 airports with a distributed antenna system to provide better service inside the terminals.

"We recognize how important it is for busy travelers to have a fast, reliable wireless service while they're on the move," said a company spokeswoman.

Sprint said it was working on improving the experience in airports, and in April partnered with Boingo to provide free access to Wi-Fi service in 35 major US airports for its customers.

T-Mobile wasn't available for comment.

Updated at 10:27 a.m. PT: Added a comment from AT&T.