[daemonologist]

If you keep the payload under 4 pounds I believe it's theoretically unregulated in the US except section 101.7 - don't create a hazard. I would still try to be approximately in compliance with part 101 though. Not a laywer.

[jacquesm]

Four pounds of hardware ingested by a jet engine is going to do a shitload of damage.

[1024core]

Exactly. Given that most birds weigh less than 4 pounds and bird strikes can take an engine out completely.

Plus, if @jacquesm says it, it must be true. ;-)

[daemonologist]

I agree, but apparently that's the rule.

[HNisCIS]

These pico balloons weigh grams.