Hitting a flock of birds can take out an engine tho.

What about hitting half a goose?

Here's some bird ingestion data for you from the certification of a GE90 Engine (large commercial airliner engine)

"As part of the required certification testing, the GE90 successfully completed both the 2.5 and 8 lb. (1.13 and 3.63 kg) bird ingestion tests on the engine’s composite blades. In October 94, four 2.5 lb. birds were ingested with the engine running at speeds required to produce 85,000 lb. (377.8 kN) of thrust at takeoff on a hot day. There was no thrust loss and the engine responded to all throttle commands during the required 20 minutes of operation following the ingestion."

https://www.easa.europa.eu/en/downloads/7799/en https://www.kimerius.com/app/download/5781574315/The+GE90+-+...

the point is birds don't need a license to fly, so balloons with that payload weight shouldn't either

Hitting a single bird can take down a plane. Here's some cockpit footage:

https://www.youtube.com/watch?v=rNqU8jfAJMQ

Here's that didn't take down the plane, but made a big hole in the canopy spewing blood and guts all over the person in the back seat with the body hitting them in the shoulder.

https://www.youtube.com/watch?v=XAn6yBJjC8g