I am seeing loaded into the schedule 5 OS 787 flights for next summer (sample date June 8) from VIE to BOS, IAD, JFK, ORD & YUL. That suggests OS will have at least 5 787s by then, up from 2 at present. Given Lufthansa's recent announcement they will take up to 7 new Dreamliners (with the Alegris business cabin seats blocked due to certification issues) by end 2025, it seems to me LH will give OS some of the 787s they are currently flying and that OS may start retiring some of its 767s.