Homeland Security Secretary Janet Napolitano warned of gridlock at Miami International Airport, which sees an average load of 100,000 passengers per day, during a recent visit to the global travel hub. Executives at the airport say they don’t know what to expect Friday because it’s not known when unpaid furloughs and other cutbacks would start thinning out the ranks of security screeners, air-traffic controllers and other federal staffers that are critical to MIA’s operations. Fort Lauderdale-Hollywood International Airport could also be affected.

Miami International’s director, José Abreu, said “no one is really sure what is going to happen” but that he expected staffing cuts to unfold gradually. But cutbacks on staffing for an airport already begging for more Customs inspectors and federal screeners will mean headaches for travelers, he said.

“During peak hours the system breaks down every day,” he said. “Now, it’ll be even worse."

MILITARY: All 780 civilian military employees at the Pentagon’s Southern Command headquarters in Doral, Homestead’s air base and at an outpost in Key West would stay home from work one day a week if the sequester stretches more than one month, spokesman José Ruiz said. The Pentagon does not expect to cut back payroll for the region’s 550 uniformed personnel, he said.

Ruiz, a civilan employee, would be one of the workers to lose a day’s pay for 22 weeks starting April 25. The unpaid furloughs would end in September.

PORTS: At PortMiami, Johnson said he has canceled travel plans to be on site when the sequester arrives. Friday typically is a busy day both for cruise ships and cargo operations.

The start of the cuts falls during a busy time for fresh produce in South Florida, adding urgency to the shipment of goods out of Latin America. That means potential impacts for both PortMiami and Port Everglades.

“March is crazy melon season — melon madness,’’ said Port Everglades spokeswoman Ellen Kennedy. “You don’t want fresh produce sitting on the docks.’’

RESEARCH: At Florida International University, the sequester has been causing problems for months.

Andres Gil, vice president for research development, said the National Institutes of Health and the National Science Foundation began tightening up on research dollars during past budget crises. With the March sequestration deadline looming, FIU has seen a general 10 percent cut in grant dollars and more difficulty getting research positions funded, Gil said.

“We have already been impacted by it. That’s what the public doesn’t realize,’’ he said. A cutback in research dollars will mean significant strain for a school that gets about $90 million a year in science and medical grants from Washington.

At the University of Miami, medical research grants account for the bulk of nearly $400 million in federal dollars the school receives each year — not counting Medicare and Medicaid payments for its hospital. On Thursday, UM issued a statement on the sequester that said in part: “Impacts will be gradual, but profound if fully implemented. Will negatively impact hospital operations, teaching and training, and research.”

Despite the ongoing spending cuts from Washington, Gil said FIU should be able to manage with fewer federal dollars. He’s working this week to find university funding for a research position after federal dollars fell through for the full-time job. “We’ll be creative,’’ he said. “We’ll get through it.”