The U.S. government is raising its security threat level to code red for commercial flights from Britain to the U.S.

That's the highest threat level. All flights in the U.S. and destined for the U.S. are code orange. It's a response to a reported terrorist plot in Britain.

British authorities thwarted a major plot to blow up "a number of aircrafts" in mid-flight between the U.S. and Britain using explosives smuggled in hand luggage.

British Prime Minister Tony Blair has reportedly briefed President Bush on the aircraft plot. Both nations are now on higher alert.

British Home Secretary John Reid says the alleged plot was significant and that extremists aimed to "bring down a number of aircraft through mid-flight explosions, causing a considerable loss of life."

London police say a number of people were arrested after a major covert operation that lasted several months was uncovered.

If you are flying today you need to be aware of heightened security requirements. The government is prohibiting any liquids, including beverages, hair gels, and lotions from being carried on the airplane. These changes took effect at 4 a.m.

Travelers should also anticipate additional security measures within the airport and at screening checkpoints.