What is a No-Fly Zone and Why Has Ukraine Called For One?

Ukrainian President Volodymr Zelenskyy has called on the U.S. and NATO allies to establish a no-fly zone over Ukraine to prevent Russian aircraft from attacking. But establishing a no-fly zone requires much more than just making a statement — military aircraft would have to patrol the skies and be ready to fire at any Russian planes that cross into the zone. Congress is divided over the issue, while officials in the Biden administration have rejected the idea, saying a no-fly zone would draw the U.S. into direct conflict with Russia.