Why planes aren't electric. Yet.

Energy density is a massive issue for aircraft, but not just the ability to lift the weight, but not losing the weight over the flight is just as big a problem when it comes to landing safety.

And let's not even start to talk about regulatory change and the snails pace that countries aviation authorities work at. 

Aviation's warming effect can actually be counteracted by selectively choosing altitudes to create or avoid contrails, but this doesn't make headlines like electric or hydrogen aircraft.