A high-profile British businessman and his family have been identified as the passengers killed when their seaplane crashed in the Hawkesbury River north of Sydney.

Experienced Australian pilot Garath Morgan, 44, died when his aircraft plunged into Jerusalem Bay, along with businessman Richard Cousins, 58.

His sons, Edward and William Cousins, aged 23 and 25, also perished in the flight, as did his fiance Emma Bowden, 48, and her daughter, Heather Bowden-Page, 11.

Richard Cousins was identified by police as the CEO of the world's largest food catering company - Compass Group.

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Cousins in September announced his retirement from the company after turning around it's financial misfortunes throughout his 11-year tenure, UK media widely reported.

He was named as the world's 11th most powerful CEOs by the Harvard Business Review this year.

- AAP