Many Americans became familiar with the term "no-fly zone" following the 9/11 attacks, when one was established around Washington, D.C., but the concept is not much older than that. The first no-fly ...

The sky is a wide-open expanse of seemingly endless open air. But even thousands of feet above the ground, there are still rules that must be followed. Planes can't simply fly wherever they wish.

Poland suggested such a zone after a major Russian incursion. But political hesitance and military shortcomings pose clear obstacles. By Marc Santora Reporting from Kyiv, Ukraine After recent ...