I believe that the Federal Aviation Regulations give unpowered craft right of way over powered craft, so it would the responsibility of any aircraft that encoun

I believe that the Federal Aviation Regulations give unpowered craft right of way over powered craft, so it would the responsibility of any aircraft that encountered the balloon to steer around it. But realistically, the odds that any aircraft would even get near the balloon are very small. Most of its flight was far above the cruising altitude for commercial aircraft. And during its ascent and descent, contact with aircraft is minimal: the atmosphere is very very very big and the combined volume of all the aircraft in the world is very small comparison.