Corporate jets would be on their own under a plan to close control towers at South Florida’s smaller airports to save federal transportation dollars under automatic spending cuts that kicked in Friday.

Towers at the Opa-locka Airport in Miami-Dade and North Perry Airport in Broward would go dark in April, leaving private pilots to navigate themselves to the runways without help from air-traffic controllers, according to officials in the two counties. The airports are popular with corporate jets, owners of private planes and others who fly aircraft too small to use Miami International Airport and Fort Lauderdale-Hollywood.

The closures are part of a nationwide plan by the Department of Transportation to pull controllers from small airports as the Federal Aviation Administration cuts $600 million from its $48 billion budget. The FAA cuts are a small part of the $85 billion set to drop out of the national budget this year under the so-called “sequestration” regimen approved by the White House and Congress in 2011.

Federal transportation officials say safety won’t be compromised, since small planes routinely land in airports without operating control towers. Even Opa-locka closes down its tower at 9 p.m. each day, while planes continue landing throughout the night.

But the lack of towers during peak time at Opa-locka, a popular spot for corporate jets and traveling executives, could upend an elite corner of air travel into the region as well as scramble operations for flight schools, banner planes, blimp operators and other companies that rely on the smaller airports. It also raises the risk of a mid-air collision if two pilots don’t communicate properly on an approach that’s currently monitored by professional air-traffic controllers.

“It becomes a safety issue,’’ said Marc Henderson, a spokesman at Miami International Airport, a county agency that also supervises Opa-locka. “Planes that are coming and going will have to be a little bit more vigilant.”

Henderson said private jets would likely shift to the Fort Lauderdale Executive Airport, which is not on the list of 189 towers scheduled to be closed by the FAA starting on April 1. Tamiami, an airport popular with private pilots, also isn’t on the list.

Two companies -— Robinson Aviation and Midwest Aviation -— currently hold contracts with the FAA for air traffic control services at nearly 200 airports throughout the country, and the contract would be scratched under the FAA cuts. Robinson runs the towers in Opa-locka and North Perry, which is Pembroke Pines.

The small tower closings are probably the most dramatic element of a wider cutback in the federal dollars that go into the nation’s aviation network, with shorter work weeks planned for air-traffic controllers and security screeners at MIA, Fort Lauderdale-Hollywood and the country’s other major airports.

Jim Marinitti, president of the South Florida chapter of the National Air Traffic Controllers union, said cutbacks on paid shifts will force the large airports to significantly restrict the number of planes that can take-off and land each hour. He said controllers plan to lose 11 days of pay between April and September, forcing big changes in how the main towers operate.

“It’s not pretty. The only way to preserve to safety is to adversely affect efficiency,” Marinitti said. “We operate in a mistake-free environment.”