American Airlines is canceling up to 720 flights in and out of Dallas-Fort Worth Airport due to lightning and the threat of tornadoes, the air carrier said on Tuesday.

American, said its planes at the Dallas airport have been at a standstill since this morning and was diverting incoming flights to nearby cities.

"They had to evacuate the air traffic control tower for about 10 minutes under threat of tornado, and that resulted in a ground stop," an American Airlines spokesman said. "We've had ramp closures because of lightning for hours now, and we had to make a tough decision."

The spokesman said American has diverted about 100 inbound flights, and is hoping to shuttle passengers to Dallas as soon as there is a break in the weather.