Non-zero: https://en.wikipedia.org/wiki/UPS_Airlines_Flight_6 > The report indic...

		icehawk 30 days ago \| parent \| context \| favorite \| on: Virgin and Qantas to ban use of portable power ban... Non-zero: https://en.wikipedia.org/wiki/UPS_Airlines_Flight_6 > The report indicated that the fire was caused by the autoignition of the contents of a cargo pallet that contained more than 81,000 lithium batteries and other combustible materials

So we just need to limit to 80,999 power banks on a plane at once