(CNN) – A new study shows circulating air on airplanes is unlikely to spread coronavirus.
The Department of Defense research concluded aircraft ventilation systems are effective at removing COVID-19 from the air.
But the study did come with several caveats.
First, it used a mannequin wearing a surgical mask to simulate a coughing passenger and assumed all passengers were masked and facing forward.
On actual flights, passengers often move their heads and move about the aisles, bathrooms and other places where they could encounter the virus.
The study also did not simulate what would happen if a passenger coughed or breathed directly onto someone else.
Researchers say testing also did not include substantial movement throughout the plane or in the airport, lounge or jetway, where air exchange rates and human interactions will vary.