Heavy Morning Fog Enshrouds Downtown Dallas

Mike Alvstad shot the above photo of downtown Dallas enveloped in fog through the window of an airplane on Tuesday morning

Image: Downtown Dallas is enveloped in morning fog, Tuesday, Dec. 9, 2014.

Downtown Dallas is enveloped in morning fog, Tuesday, Dec. 9, 2014. The National Weather Service issued a dense fog advisory Tuesday morning for the Dallas-Fort Worth area. The heavy fog has delayed some flights in North Texas.Mike Alvstad via AP

Dec. 9, 2014, 10:18 PM UTC / Updated Dec. 9, 2014, 10:02 PM UTC

Mike Alvstad shot the above photo of downtown Dallas enveloped in fog through the window of an airplane on Tuesday morning. The American Airlines mechanic told NBC News he snapped this photo just before his flight descended into Dallas/Fort Worth International Airport. Due to heavy fog conditions, flights headed to the airport were held on the ground at their departure airports.

— Emmanuelle Saliba

Image: Crossing-guard Felix Robles stops traffic as students cross the street during heavy fog — Crossing-guard Felix Robles stops traffic as students cross the street during heavy fog in Odessa, Texas, on Tuesday, Dec. 9. The National Weather Service issued a dense fog advisory Tuesday morning for the Dallas-Fort Worth area.Courtney Sacco / The Odessa American via AP