Cigarette butt causes Pittsburgh airport smoke

"There's no threat involved in any of this," Jenny said. "It's not like anybody was trying to plant a bomb or anything like that."

The D concourse is one of four lined with dozens of airline gates at the X-shaped terminal about 10 miles west of the city. Delta, United and American airlines flights that normally use the concourse were sent to gates in other parts of the airport, but there were no reports of major delays.