Croatia Airlines open booking for all domestic and plenty of international routes from middle of May.
Right now it is possible to book flights on all domestic routes, from Zagreb to Dubrovnik, Brac, Split, Zadar and Pula, starting from May 18th. By the information from national Civil Protection HQ, it looks like Croatian national carrier could operate domestic routes from mentioned date!
A lot of international routes are now open for booking again from the same date (May 18th), but it is still early to talk about possibility for their launch. Those routes depends on COVID-19 situation in the countries where OU should fly. COVID-19 is not the only problem, there are also travel restrictions currently active in many European countries.
We can now just monitor decisions from the countries where OU is originally flying, since all airlines are depending on it right now.