The control tower at Tulsa International Airport was evacuated twice on Wednesday; once in the afternoon and again the same night.
The Tulsa Fire Department said nasty fumes caused the tower's first evacuation when a solvent used by a contractor made a few people sick.
The tower then re-opened, briefly, but was evacuated a second time so the air could be tested.
Due to the evacuations, some American Airline flights are experiencing some delays. A TIA spokesperson said the decision to fly in and out of Tulsa was left up to each airline.
As was the case with the first evacuation, Kansas is handling air traffic in and out of Tulsa.
During the first evacuation, three people complained of feeling sick and were checked out by medics but refused to go to the hospital.
Video from Osage SkyNews 6 HD showed at least three fire trucks and an ambulance parked near the tower.