U.S. authorities are watching warily but have made no new plans to protect travelers during the busy Thanksgiving week despite threats from Islamic State to strike targets in New York and Washington, two law enforcement officials said Friday. 
 
 The deadly rampage in Paris and the bombing of a Russian passenger jet in the last three weeks have put U.S. law enforcement and aviation security on heightened alert for another possible terrorist attack. 
 
 But U.S. intelligence officials have seen no indications of credible plots in the works beyond the bellicose videos and other rhetoric posted online by Islamic State militants. The officials spoke on the condition of anonymity to discuss internal assessments. 
 
 "The threat level continues to be the same as it was last month," said Ali Soufan, a former FBI agent who worked on terrorism cases and now runs a security consulting firm in New York. 
 
 After a bomb brought down a Russian Metrojet flight over the Sinai Peninsula on Oct. 31, killing 224 people, the Transportation Security Administration rolled out stricter screening requirements in overseas airports that are the last point of departure for U.S.-bound flights. 
 
 "As the investigation and our own review of the crash proceeds, we will continually assess our aviation security enhancements, and consider whether additional changes are appropriate," Department of Homeland Security Secretary Jeh Johnson said at the time. 
 
 Russian officials confirmed this week that the jetliner had been blown apart by a homemade bomb with the explosive power of two pounds of TNT smuggled on board. 
 
 In a video released Thursday, Islamic State operatives threatened to launch an attack on New York City and showed images of Herald Square and Times Square. In response, Mayor Bill de Blasio said there is no specific and credible threat, and the city "would not be intimidated." 
 
 The New York Police Department this week deployed the first 100 officers of a long-planned force of about 500 anti-terrorism officers called the Critical Response Command. The new force is headquartered on Randalls Island on the East River in order to have quick access to three of the city's five boroughs. 
 
 A separate video released by Islamic State militants in Iraq after the Nov. 13 attacks in Paris warned of attacks in Washington. But security already is tight in the nation's capital. 
 
 Al Qaeda, which was responsible for the Sept. 11 attacks, has sought to launch an attack on American soil since the 1990s. It's most lethal offshoot, Al Qaeda in the Arabian Peninsula, based in Yemen, has repeatedly sought to bring down U.S. airliners. 
 
 Islamic State, which now has eclipsed Al Qaeda, recently shifted its attention from seizing and controlling territory in Syria and Iraq, its self-declared caliphate, to actively plotting attacks against its foreign enemies, especially France, Russia and Iran-backed Hezbollah in Lebanon. 
 
 Counter-terrorism officials warn that the United States could be next on the list. 
 
 "Do they have the intention? Yes. Problem is, do they have the capability?" Soufan said. 
 
 The current intelligence assessments are in contrast to security alerts issued shortly before the Fourth of July weekend. At the time, U.S. security agencies picked up intelligence suggesting possible attacks and urged local police to be vigilant during parades, concerts and fireworks displays. 
 
 An estimated 25.3 million Americans will board an airplane in the 12 days around Thanksgiving, according to Airlines for America, an airline trade association. That's 3% more than last year's holiday season and the highest number of passengers since 2007. 
 
 Each year, the holiday season stretches the capacity of airport screeners at the TSA. They face the challenge of preventing weapons and explosives from being taken on jets without delaying passengers. 
 
 During the 2010 Thanksgiving travel crush, passengers faced intrusive pat-downs and body scans following a foiled attempt by Al Qaeda's affiliate in Yemen to hide makeshift bombs inside printer cartridges carried in the hold of passenger jets bound for Chicago. 
 
 The pat-downs have since been scaled back in favor of new aviation security systems, including additional database checks of travel histories, more robust screening of cargo and baggage overseas, and other measures. 
 
 brian.bennett@latimes.com 
 
 Follow me @ByBrianBennett on Twitter 
 
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 With the highest number of passengers expected to hitch a ride on U.S. airlines on Thanksgiving since 2008, security officials are on heightened alert to protect our nation’s skies and railways. 
 
 The Port Authority of New York & New Jersey tells ABC News it is on heightened alert in light of the deadly attacks in Paris. The Port Authority will be increasing patrols and inspections in New York City-area airports, bridges, tunnels, railways and the World Trade Center. Travelers, as usual, are being asked to report any suspicious activities to police. 
 
 Railway passengers nationwide will also see a significant increase in security. 
 
 Amtrak says it is working with local, state and federal law enforcement to gather intelligence and establish robust security measures not just at the stations, but on trains and along the tracks. 
 
 An Amtrak spokesperson tells ABC News additional K9, uniform personnel and long guns have been deployed at various points of Amtrak’s service and employees have been debriefed with guidance regarding active shooter incidents. 
 
 The Transportation Security Administration is not divulging specifics beyond the ordinary, but says it has measures in place, both seen and unseen, to protect the millions of Americans traveling nationwide. 
 
 Passengers at busy airports such as LaGuardia and JFK in New York can expect longer waits, even with additional staffing at checkpoints. 
 
 According to TSA officials, the security administration screens nearly 2 million passengers daily and on the days leading up to Thanksgiving that number is expected to increase nearly 40 percent nationwide. That influx would spell the busiest travel season in its history. 
 
 Significant additional layers of security are routine during the American holiday season, but the recent events in France are sure to contribute. 
 
 ABC News' Erin Dooley contributed to this report.
– Officials say there are no specific threats to Americans over the Thanksgiving holiday, but travelers can expect heightened security and extra delays regardless. The Los Angeles Times cites two anonymous law enforcement officials, who say there are no additional security measures being put in place for holiday travelers to address recent Islamic State videos threatening attacks on New York City and Washington DC. Experts have deemed those threats not credible. However the officials note law enforcement and aviation security are already on heightened alert following the attacks in Paris and the destruction of a Russian passenger jet over Egypt. ABC News reports travelers can expect extra layers of security at airports and train stations—typical during any holiday season. There will be increased patrols at airports, tunnels, trains stations, and more in New York City. And Amtrak is deploying additional security personnel at various locations. Officials say the extra measures are necessary because of the high number of travelers over Thanksgiving. According to the Times, an estimated 25.3 million Americans will fly somewhere next week—the most since 2007.