An airplane is a big closed conductive tube, not connected to the ground. There's nothing to worry about. I'd happily fly on those days.
As for why we worry about the storms on the ground - the main effects of Geomagnetic storms on the ground involve DC currents generated in power grids that span hundreds of miles, at the ends of those transmission lines, are transformers engineered to most efficiently use the transformer steel by almost pushing it to saturation, at which it rapidly loses the ability to contain more lines of flux. This saturation can then allow almost unlimited amounts of current to flow, turning the transformer into a space heater, connected to gigawatts of power. Things can then very rapidly get out of hand, circuits fault, opening lines, causing power to be diverted elsewhere, until the entire grid goes down.
No such issues can happen in an airframe.
