For those who might want to book domestic flights in Greece in 2026, Sky Express, the second largest Greek airline, is currently offering up to 50% off on some flights. (Especially, from what I've seen, on the first or last flights of the day.)
https://www.skyexpress.gr/en/flights-up-to-fifty-percent-off-oct25-en
I have no commercial relationship with Sky Express.
Also, keep an eye on the Aegean website's "Flight Deals" page and expect, as every year, discounts on Black Friday. Usually up to 60%, or even 70%. This offer is usually only valid for 24 hours.