[wkat4242]

Since the kindles with 3G have disappeared, the need for airplane mode for actual airplane use is a lot less though. Where I am most airlines permit WiFi use and even offer it themselves in flight. Only mobile network connections still have to be switched off.

[toyg]

Airplane mode is mostly a power-saving feature, because WiFi drains the battery pretty hard. As others said, leaving wifi on will kill your kindle in a week or so, whereas it can go on for months without it.

[wkat4242]

That's not my experience. My kindle paperwhite (latest version until yesterday) lasts at least 3 months with WiFi on. I never turn it off.