He was the youngest of three brothers in Glasgow who, from 1898, revolutionised heating, cooling and ventilation in shipping, railways, aircraft and public buildings around the world.

In 1901 they formed their own company, Thermotank, based in Glasgow and innovated methods of heating, cooling and ventilating ships of all classes, trains, and in due course aircraft to ensure fresh air and controllable temperatures efficiently for the benefit of crews, passengers and cargoes.

[4][5] Frederick Stewart's first class organising ability and foresight in long-term planning was recognised by the commercial and industrial world.

[4][5] In June 1948 he was appointed a member of the UK committee which guided the development of the Festival of Britain which opened in 1951, its main venues being London and Glasgow.

He was closely linked to Churchill's Cabinet and to the work of fellow industrialist Sir James Lithgow, the Controller of Merchant Shipbuilding.

Sir Frederick made substantial donations of £20,000 towards the development of the Engineering Department at Glasgow University.

He phoned the aerodrome to cancel his reservation and ordered the same number of seats on the following plane leaving three hours later.

[9] Sir Frederick was a bachelor and shared the family's home at 8 Lancaster Crescent, Great Western Road, Glasgow and at Craigrownie Castle,[10] Cove, overlooking the Firth of Clyde, until his death in 1950, age 72.