Before the Avengers fight against each other in the airport, why was the airport evacuated? Did Tony Stark (he sided with the government) order the evacuation, due to his rival arriving? Or did the airport authorities order the evacuation?
An alarm sounds right before before the airport battle, telling everyone to evacuate. Falcon states "Stark", to which Ant-Man responds "Stark?" and Captain America nods and tells everyone to suit up. We can infer that Stark had found the Captain's group and was evacuating the airport to reduce the risk of civilian casualties if it turned into a fight. Which it did.