New York -Millions of U.S. travelers flying during the busy Fourth of July holiday weekend will face heightened security due to the deadly attacks at Istanbul’s main airport, officials said on Wednesday, adding to potential delays.

Airport officials were hesitant to reveal specific safety measures taken following Tuesday’s attacks by suspected Islamic State militants, which killed 41 people and wounded 239 at Europe’s third-busiest airport, but increased vigilance appeared to have resulted in at least one airport disruption.

A terminal at John F. Kennedy International Airport in New York was briefly evacuated on Wednesday morning while police, including a bomb squad, investigated a report of a suspicious package.

The Port Authority of New York and New Jersey, which oversees operations at the three major airports in the New York City area, said in a statement that police had added “high visibility patrols with tactical weapons and equipment.”

The agency said it had already put in place counterterrorism patrols at various transportation hubs in the region following the mass shooting in Orlando earlier this month.

Agencies in charge of other major airports, including Reagan and Dulles in the Washington, D.C. area, Logan in Boston, O’Hare in Chicago, Hartsfield-Jackson in Atlanta and Dallas/Fort Worth, declined to offer operational details but emphasized that security remains their top priority.

“Logan maintains an enhanced security posture,” said an spokeswoman for the Massachusetts Port Authority. “There are many elements that are seen and unseen.”

A record number of U.S. travelers are expected between June 30 and July 4, according to AAA, which projected nearly 43 million Americans would leave home.

The vast majority of those travelers will go by car, AAA said, but 3.3 million are expected to fly. That is more than 25 percent higher that the 2.6 million AAA projected to fly during Memorial Day weekend in May, when complaints about long security lines were widespread.

Like the attackers at Brussels’ airport in March that killed 16 people, the three Istanbul suicide bombers appear to have struck in a public area outside the first passenger checkpoint.

The attacks have reignited debate over whether airport security and screening should extend into public spaces, despite the increased inconvenience and questions about the effectiveness of such a move.

The Transportation Security Administration, which handles screening at U.S. airports, saw mounting criticism this spring from travelers who reported enormous wait times and lengthy security lines stretching through terminals.

The TSA has seen cutbacks in recent years, even as screening procedures were tightened after undercover investigators were able to smuggle weapons and fake bombs through dozens of checkpoints without detection. Those factors have added to the delays.

The agency has responded by hiring additional screeners and increasing overtime.