The Chimaeric Demons didn't wait much before going into action, following Erik's order.
Basically, the moment the president's daughter stepped out of the plane stairs, they moved.
Not all of them were on the landing site, but first the Chimaeric Demons that were the furthest from the sight got closer, then the others moved.
There were actually few people there. The guards and the very few selected to bring the woman's stuff and empty the plane, and half the guards were in truth Chimaeric Demons.
Regardless, with the other clones in the form of bugs approaching them, those who hadn't been replaced yet got surrounded.
As that happened, the guards noticed something was wrong but didn't act fast enough for them to make a perimeter around the president's daughter.