British authorities' arrest Thursday of two dozen suspects in what they called a terrorist plot to destroy to 10 planes on their way to the United States created huge disruptions at airports as officials scrambled to implement new security measures.

In question-and-answer form, this is a brief look at the situation and its implications for air travel.

Question: What are authorities saying about the attack that was planned?

Answer: British officials say terrorists aimed to simultaneously blow up 10 aircraft heading to the U.S. using explosives smuggled in hand luggage. U.S. Homeland Security Secretary Michael Chertoff said the terrorists planned to use liquid explosives disguised as beverages and other common products and set them off with detonators disguised as electronic devices.

Question: British officials arrested 24 people early Thursday. Is the threat over?

Answer: No. Chertoff said Thursday that "we cannot assume that the threat has been completely thwarted." The investigation into the plot is ongoing. In steps that underscored how seriously it was taking the case, the Bush administration posted an unprecedented code-red alert for passenger flights from Britain to the U.S. and banned liquids from all carry-on bags.

Question: But I've got a flight to catch in the next few days. How much more time should I allow in arriving the airport?

Answer: To be on the safe side, a lot. Federal officials advise checking with your airline and airport to determine how much time is needed for your flight. United Airlines said passengers should arrive at least three hours early for all flights. In Minneapolis, Northwest Airlines advised passengers to arrive two hours before domestic flights and three hours before international flights. And beginning Friday, passengers will go through double screening to make sure they're not carrying liquids onto planes — with carry-on luggage getting checked not only at the main security checkpoint, but also a second time at the boarding gate.

Question: Do the changes affect all flights in the U.S.?