Passengers in the United States are facing heightened security at airports Thursday after British authorities uncovered a terror plot aimed at airlines.

British authorities say they thwarted a terrorist plot to simultaneously blow up several U.S.-bound aircraft using explosives smuggled in hand luggage. While security was raised to the highest level in Britain, U.S. officials raised the terror alert level to its highest level of red for commercial flights from Britain to the U.S. The alert for all flights coming and going from the U.S. was also raised slightly to orange.

Two U.S. counter-terrorism officials say the terrorists had targeted United, American and Continental airlines. American Airlines has since canceled six flights between the U.S. and London to accommodate delays at London's Heathrow Airport. U.S. Homeland Security Secretary Michael Chertoff has said there is no indication of current plots within the U.S. Meanwhile, British police have arrested at least 24 people in connection to the terror plot.

Officials say people looking to travel should expect delays and more security measures at airports. Liquids, including beverages, hair care products and lotions have since been banned from all carry-on luggage in both Britain and the U.S.