The Port Authority of New York and New Jersey and Delta Air Lines have reached a nearly $4 billion deal to redevelop LaGuardia Airport Terminals C and D, the authority and Gov. Andrew M. Cuomo announced Thursday.

After its meeting Thursday, the Port Authority’s Board of Commissioners moved to contribute $600 million to support the combining of current Terminals C and D into one Delta facility the airline would lease through 2050. The authority’s investment will leverage about $3 billion in Delta’s financing of the new facilities, Cuomo said in a Thursday news release.

“LaGuardia is one of the premier gateways into New York, but for too long its antiquated and dilapidated appearance has obscured its role as a key driver of New York’s economy and transportation hub,” Cuomo said. “Replacing these outmoded terminals is a major step forward in our re-imagining of LaGuardia into a 21st century, world-class airport worthy of the Empire State.”

The Delta terminal deal was announced less than a year after the unveiling of a grand plan to unify the airport. The ongoing overhaul of LaGuardia’s central terminal, Terminal B, has been estimated to cost about $4 billion.

That project is slated to be done by 2022, according to LaGuardia Gateway Partners, its developer.

Terminal C and D’s reconstruction — considered the last part of the master airport plan — is slated to begin after environmental review and approval by the Federal Aviation Administration, Cuomo’s office said.

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Although this is a step in the right direction, nonprofit Global Gateway Alliance, which advocates for better airports, said the Port Authority needs to adhere to greater financial transparency so the public can hold accountable those in charge of remodeling the airport.

“It’s time now for partners to bring greater transparency to the overhaul and build confidence in the project by posting clear budgets and timelines to the project website, and updating it regularly so the public can keep track,” the nonprofit’s chairman Joe Sitt said in a news release.