as I have been waiting for ATH-HER schedules in April to be published. This has now been done.
It seems as though Aegean doesn’t add all the flights for the new season on one day but uses the drip feed method. Most of the summer schedules 2017 from March 24, 2017 through to end of October/early November have now been released including the domestic flights to/from the Greek Islands.
I notice that many flights are given OA prefixed numbers replacing the usual Aegean A3 prefix that we are used to. This is in addition to the many original OA flights operating. There is probably some legal reason for the many additional OA flights. If you happen to earn frequent flyer miles with other members of the Star Alliance (of which Aegean is a member) you will not earn them on OA flights, unless the flight is stated as "operated by Aegean".
Aegean took control of Olympic several years ago but retained its branding.
Just a word of caution, several seasonal routes in summer 2016 have not been renewed by Aegeanair for this year. Two of which I am aware are axed: Athens-Oslo and Athens-Palma de Majorca. UK flights seem intact.