The coronavirus pandemic is bringing the world's airlines to their knees. The Trump administration's decision on Wednesday to suspend travel between the U.S. and the European Union's Schengen area is unprecedented. But how is this shock different from the aftereffects of the Sept. 11, 2001, terrorist attacks? On the one hand, the 9/11 attacks changed airports and airlines in noticeable ways, such as new security protocols and armored cockpit doors. On the other hand, the viral pandemic's effects are more widespread and universal for the world's airlines than the fallout from the 9/11 attacks.