[masklinn]

> What I think he's talking about is NOT a conventional plane with a battery simply replacing the gas tank, but instead essentially a flying battery, where 90% of the plane's mass is battery.

Weight is the premium on planes, so the 10% of non-battery you're talking about is a full plane minus fuel tanks. An E-170 is 21t of empty plane, up to 9t of fuel and up to 36t total (MTOW). Given batteries have 1% the energy specificity of aviation fuel (so you need 100 times the weight in batteries for the same stored energy), the math doesn't quite work out.

> This sounds ridiculous at first

And at second, and at third.

> when you consider how cheap electricity is compared to jet fuel

Doesn't compensate the problem of needing a plane 10 times as heavy with 1/10th the payload.

> as well as the other benefits the OP mentioned

Which don't really make sense, lower air density means your turboprops have nothing to work with, there's no such thing as turbofans let alone turbojet so the gains in drag are killed by the inability to actually go forward.