The Transportation Security Administration detected the suspicious package at 6:17 a.m. during screening of checked baggage in Terminal A, which is home to American Airlines at the airport, TSA spokesman James Fotenos said.
"To ensure the safety of the traveling public, the nearby security checkpoint was temporarily closed," Fotenos said.
Ron Marsico, a spokesman for the Port Authority of New York and New Jersey, which operates the airport, said one security checkpoint in Terminal A was shut down, as was the ground floor area where the bag was being screened. The rest of the terminal operated normally, he said.
A police bomb squad cleared the monitor and normal operations resumed at 8:16 a.m.
Computer monitors normally emit small amounts of radiation and there was never any danger, FBI agent Bryan Travers said.
The monitor was being shipped to the same destination as its owner, who was already in flight, Travers said.
It wasn't immediately known how many flights were delayed by the closure. Marsico said some flights may have been moved to different gates.
Several travelers arriving on flights from Fort Lauderdale, Fla., Charlotte, N.C., and Halifax, Nova Scotia shortly after the checkpoint was reopened said their flights arrived on time or close to it, and that no announcements were made about the closure.