Having spent considerable time in a NORAD facility in Alaska, I find this tale of interagency collaboration interesting, fascinating as well as disturbing.
NORAD headquarters is operated jointly by Canadian & American military forces and this was their dilemma:
"An initial assessment from NASA suggested the debris field [when the balloon would be shot down] could be as large as 100 by 100 kilometres, increasing the possibility of inadvertent casualties on the ground. That estimate was later modified to 10 by 10 kilometres, still a wide swath of landscape. And he stresses that a lot of valuable intelligence was gathered — both while the balloon was in the air and after it was brought down — by waiting until it trundled off the U.S. Atlantic coast."
Read the National Post's reflection on the incident and why Canadian Forces chose not to shoot it down but allow it to pass into American airspace.
Photo by Chad Fish via The Associated Press