> People keep saying a lightweight craft under six pounds poses no threat to commercial aviation, but is that really true?

True enough for the extremely risk-averse FAA.

> there are lots of sensitive measurement devices, like a pitot tube, that I imagine could fail if a balloon hit it. (For reference, Aeroperu 603 was brought down by tape that wasn't removed from the plane.)

Tape over all of the multiply-redundant static ports on the aircraft. We don't treat tape as a critical threat to aircraft.

The 737-MAX has three pitot tubes and six static ports, deliberately placed on both sides of the aircraft. (https://www.researchgate.net/figure/Boeing-737-NG-and-MAX-pr...)