This is going to be huge. Assuming the USB ports on airplanes are powerful enough to charge the rMB with the USB-C to USB adapter, then this will be welcomed by so many people. Even if it can only keep its current battery level steady, then I think that will be fine. Most economy seats don't have power ports, but a USB port is always available. And even general, being able to charge a laptop via USB opens it up to so many possibilities.