Travelers in New York are expected to encounter tighter security at airports throughout the area Thursday after authorities in London uncovered a major terror plot aimed at airlines traveling from Britain to the United States.

The Department of Homeland Security has raised the U.S. airline terror threat level to the highest level point. All flights from Britain to the United States are now at code red level, and all flights within or leaving the United States are at high, or orange level.

Police arrested 21 people overnight in London and surrounding areas following a major counterterror operation. The terrorists' goal was to blow up trans-Atlantic planes in mid-flight using explosives in carry-on luggage, said the London police.

Homeland security officials said that the plot appeared to have been well-planned and well-advanced, with a significant number of operatives. The terrorists planned to carry the components of the bombs, including liquid explosive ingredients and detonating devices, disguised as beverages, electronic devices or other common objects.

The plot was aimed at flights to New York, Washington and California, all major summer tourist destinations, officials said.

Searches for other suspects are underway, with an estimated 30 more people still at large.

According to U.S. counterterror officials, the targets of this terrorist attack include major U.S. airlines such as United, American and Continental Airlines.

American Airlines canceled six flights between the United States and London, including one from JFK Airport and one to the same airport.

Officials of homeland security have forbidden passengers traveling in the United States from carrying liquids like beverages, hair gels and lotions onto both domestic and international flights.

At a news conference, Homeland Security Secretary Michael Chertoff apologized for any problems passengers may face, but said the changes are meant to keep them safe.

"We recognize these measures are going to be inconvenient. But they are proportionate to the very real threat to the lives of innocent people that was posed by this plot," he said. "And what is important here is that we are taking every prudent step to thwart new tactics of terror."

Airline passengers are advised to arrive two hours early for all domestic flights. They will also have to remove their shoes as part of the X-ray screening process. No beverages are allowed on board, including drinks purchased at the airport. Toothpaste, perfume, shampoo, hair gel and suntan lotion are also banned.

Source: Xinhua