U.S. airlines Monday said their flights and schedules were unaffected by the U.S. State Department alert issued Sunday to warn American tourists of the potential for attacks by al-Qaeda and other groups in Europe.
“Our flights in and out of Europe are continuing as scheduled, and at this time we don’t foresee any changes to our operation,” a spokeswoman for Delta Air Lines said.

An American Airlines spokesman said there has been no impact on the carrier’s 40 round-trip daily flights between the United States and Europe.

United Airlines, which has about 30 daily flights to Europe, said its schedule was normal.

The U.S. alert urged travelers to take precautions when they travel. The threat that prompted the State Department’s alert was outlined last week in media reports, which said militants were plotting coordinated attacks on European cities.

U.S. airline shares were broadly weaker Monday with the Arca airline index down 1.52 percent.