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 last June it would contract with a subsidiary of 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 in the fall. When that deadline came and went, the Port Authority said the complimentary 30 minutes of 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 currently 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 still have to rely on paid or advertisement-sponsored Wi-Fi, which is 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 the Global Gateway Alliance called the Port Authority's work to get free Wi-Fi installed "a major win for passengers" and a necessary move to keep New York City's busy airports up to speed with the rest of the traveling world.

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 wireless company and the Port Authority are "working together to help expedite the placement of the service in the remaining terminals." The Port Authority did not offer a timeline of when that project will be done.

The upgrades will mean higher-speed Internet and better signal connections at the airport terminals, the Port Authority said. Boingo subsidiary New York Telecom Partners LLC will install, operate and maintain the expanded network at no cost to the Port Authority, a spokesman said, and the agency will take home a share of the profits.