Roads inside LaGuardia Airport are badly congested, federal officials said Wednesday as they recommended that people arrive at the airport 2 to 2 1⁄2 hours before their scheduled departure time.

“Travelers may want to arrive even earlier during holiday travel periods such as Labor Day and Thanksgiving weekends,” the Transportation Security Administration said in a news release.

TSA said it had seen an increase — but did not give specifics — in the number of people arrive late at its security checkpoints at LaGuardia, which is in the early stages of a massive reconstruction project.

The late arrivals told screeners “that their drive to the airport was impacted as a result of construction, which at times, slowed traffic from the main highway,” TSA said.

The additional time does not include getting to the airport, TSA said.

“You’ll need to park [or get dropped off], get a boarding pass, check baggage and then get into the checkpoint line,” TSA spokeswoman Lisa Farberstein said.

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“It all takes time. And on a holiday weekend, more people are coming to the airport, so it will take longer because more people will be there,” she said.

The construction of a new Central Terminal and a new parking garage at LaGuardia that began in early July has caused a change in traffic patterns.

The closing of the current garage and two parking lots has forced drivers to find alternatives, such as parking at a lot farther away and taking a free shuttle bus.

In all, there will be a least 2,000 fewer parking spaces, down from 6,400 pre-construction, at the airport during the next two years, said the operator of the airport, the Port Authority of New York and New Jersey.

The Port Authority had no immediate comment. While the port agency runs the airport, the main terminal reconstruction is being done by a private contractor not directly under its control.

The demolition and reconstruction of the main terminal, used by eight airlines, should take several years, and there may be an overlap when Delta begins reconstruction of its terminal, just east of the main terminal.