9/11 how many days was the U.S.'s airspace closed for?

Question

how many days was the U.S.'s airspace closed for after the tragedy?
international flights and domestic flights.,.....

Answer 1

It was never closed down.
Recall that the government let flights out to go to Saudi Arabia.

Answer 2

It was closed to commercial FAA Part 121 flights (without special permit) for 3 days if memory serves me. Charter flights (FAA Part 135) was open sooner (I believe 2 days.) Charter flights were allowed even sooner for such things as emergency medical situations like the organ donor program.