Complex sentence: The "Vistafjord" served under Norwegian-America and then chartered to Cunard in 1985 until 1995 when she was purchased by Cunard, which at the time owned by Kvaerner, a Norwegian company, and so remained the "Vistafjord".
Split into simpler sentences: The "Vistafjord" served under Norwegian-America until 1995 when she was bought by Cunard. At the time Cunard was owned by Kvaerner, a Norwegian company, and so remained the "Vistafjord".