During the evening commute last week, drivers found themselves in massive traffic on the ramps and roads inside LaGuardia Airport.

It was one of the most recent signs of the change coming to LaGuardia, as construction on the airport’s $4 billion renovation, first unveiled a year ago by Gov. Andrew Cuomo, has begun. And now, one of the project’s significant question marks — whether Delta Air Lines would participate in the airport makeover — has been answered.

Under a new agreement, Delta will turn its two old terminals, known as C and D, into one new one located closer to the Grand Central Parkway and connected with LaGuardia’s new central hall. The airline will be responsible for $3 billion of the cost, with the state providing $600 million, mostly toward infrastructure like roadways, parking and an electrical substation.

The deal is good for Delta, which hopes for revenue gains from more retail and restaurant options and increases in the number of passengers. It’s good for travelers who use LaGuardia. But it’s great for New York. The state is contributing just a sixth of the estimated cost, and Delta is responsible for construction and cost overruns.

Now that construction plans are set, Delta and the Port Authority have to agree on a long-term lease for the new terminal, including revenue sharing terms. Right now, Delta has no guarantees that the Port Authority, which operates the airport, will change the perimeter rule,which restricts most flights to within 1,500 miles. Nonetheless, the time has come for that change.

Now we know LaGuardia, which in 2014 was famously labeled as a Third World airport by Vice President Joe Biden, will get a full makeover. We still don’t know, however, whether an AirTrain from Willets Point will become a reality. And even with the traffic backups that have occurred with the start of the parking-lot construction, the worst of the traffic detours have yet to come.

Clear communication between the Port Authority and the public will be key. But each step is one closer to a moment when we can land at a First World LaGuardia Airport.