The Associated Press

NEW YORK CITY — Passengers in the United States coped with heightened security at airports Thursday after authorities in London uncovered a terror plot aimed at airlines traveling from Britain to the U.S.

American Airlines canceled six Thursday flights between the United States and London to accommodate the delays at Heathrow airport, spokesman John Hotard said.

American nixed three London-bound morning flights, one each from Chicago, Boston and New York's John F. Kennedy International Airport. To balance those cancellations, the airline also dropped three afternoon or evening flights scheduled to travel from London to those U.S. cities, Hotard said.

Hotard said the remaining 13 flights in each direction were expected to run from 1 1/2 to 3 1/2 hours late.

The cancellations were due to scheduling delays and not a result of possible threats to the flights, he said.

"We're going to be flying out of Heathrow today," Hotard said. "It's just that because it's so congested right now."

In response to the terror plot, the U.S. government raised its threat warning to the highest level for commercial flights from Britain to the United States and raised slightly the alert for all flights coming or going from the U.S.

The government said it was banning beverages, hair gels and lotions from flights, explaining only that liquids emerged as a risk from the investigation in Britain.

Delta Air Lines spokesman Anthony Black said Thursday morning that operations would continue normally and there would be no flight cancelations. But Delta was expecting delays on flights coming from the United Kingdom because of heightened security there, Black said.

Black said Delta was cooperating with domestic and international security authorities but declined to give details on security procedures.

He also said he did not know if the alleged terrorist plot involved any Delta flights.

Most European carriers canceled flights to Heathrow because of the massive delays created after congestion built up rapidly, after authorities enforced strict new regulations banning most hand baggage.