Question

Air is a poor conductor of electricity. but air allows current to pass through during a thunder lightning. WHY???

Answer 1

Air particles also contains electrons but in less amount therefore it act as insulator. When thunder lighting pass through air most of it's energy is wasted due to insulation. The part of light we see is the conducted part of electricity which has less energy than the energy produced on it's occurrence.

Answer 2

Answer:

When the electric field is high enough, the air partially ionizes, at which point there are free electrons to carry current and the air becomes, essentially, conductive. ... So with large voltages it is possible to generate electrons that can move freely in a gas and conduct electricity - as in the example of lightning.