[SkiBum]

What does this mean? Is Pakistan refusing to allow overflights by U.S. military aircraft? Is this a piece of disinformation? Who made the announcement?

[Zeroisanumber]

No, it means that something big is moving through their airspace and they don't want interference from non-allied countries. I would guess that it's some kind of big coalition military transport, barring that it's an attempt to move civillian planes out of the way of incomming warplanes and criuse missles. Without more information it's impossible to be sure.