New York City's major metropolitan airports have missed a second deadline to offer 30 minutes of free Wi-Fi across all terminals, but the Port Authority is optimistic the installation will be completed soon.

The Port Authority, which operates the airports, announced in June it would contract with a subsidiary of Los Angeles-based Boingo Wireless Inc. to upgrade its wireless network and offer travelers 30 minutes of free Wi-Fi at all terminals at Kennedy, LaGuardia, Newark Liberty International and Stewart International airports, beginning last fall. When that deadline came and went, the Port Authority said the complimentary Wi-Fi would be available by the end of March.

Travelers passing through terminals B and C at Newark, 4 and 8 at Kennedy, and A and B at LaGuardia now have access to 30 minutes of free Wi-Fi around the clock, the Port Authority said. And JetBlue offers free Wi-Fi at Terminal 5, its home at Kennedy.

But fliers going to Terminal A at Newark, terminals 1, 2 and 7 at Kennedy, C and D at LaGuardia, and the main terminal at Stewart, in Newburgh, must still rely on paid or advertisement-sponsored Wi-Fi, available about half the time, the Port Authority said.

To use the sponsored service, passengers have to either watch a video or download an app, which can take several minutes.

Manhattan-based travelers advocacy group Global Gateway Alliance called the Port Authority's work to get free Wi-Fi installed "a major win for passengers" -- and necessary to keep the city's busy airports up to speed with the rest of the traveling world.

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But Alliance chairman Joe Sitt said in a statement, "full implementation, planned first for fall and then March, is overdue."

A Boingo spokeswoman said by email that the company and the Port Authority are "working together to help expedite the placement of the service in the remaining terminals." The Port Authority said it is hoping to "have this done as soon as possible," but did not offer a timeline.

The upgrades will mean higher-speed Internet and better signal connections at terminals, the Port Authority said. Boingo subsidiary New York Telecom Partners LLC is investing $3.8 million in the upgrade, which comes at no cost to the Port Authority, spokesman Ron Marsico said, adding that the agency will share in the profits. Wi-Fi users who go beyond the free half-hour, where available, pay for hourly, daily or unlimited monthly service.