Travel Security Heightened for 4th of July

A day before millions of travelers are expected to hit the road, rails or sky for the long Independence Day weekend, Homeland Security Secretary Jeh Johnson says Americans should expect to see more security in public places during their holiday.

"The American public should expect to see, this July 4th weekend, an enhanced security presence at airports, train stations and other transit centers across the country by TSA and state and local law enforcement as well as security personnel generally," he said at a Senate Judiciary Hearing Thursday morning.

In addition to federal efforts, several airports throughout the country have said they are beefing up security in the wake of the attack in Istanbul.

The cities of Miami, Indianapolis, Atlanta, San Francisco, Los Angeles and New York have all said they are adding extra security for the weekend.

Los Angeles International Airport says it is expecting a record number of travelers and that they have more K-9 Units, police personnel and traffic enforcement units in place.

The Port Authority of New York and New Jersey told ABC News it has added high visibility patrols equipped with tactical weapons and equipment at Kennedy, LaGuardia and Newark Liberty airports.

The Transportation Security Administration has VIPR teams deploying to airports across the country.

The VIPRS -- a team of behavior detection offers, explosive experts, and air marshals -- were created partly in response to a series of high-profile foreign train attacks in the early 2000s. They often work special events that need extra security to deter acts of terrorism.

Airports across the country are already adding security to transit centers as Turkey is reeling from an attack that killed 43 people at the nation's largest airport.

Hopper, an airfare prediction app, is predicting Las Vegas, Washington D.C., Chicago and New York to be the most popular destinations for holiday travelers this Independence Day.

ABC News' Becky Perlow, Erin Dooley, Ali Weinberg and Whitney Lloyd contributed to this report.