The combined turnover of Bond and Helikopter Service, based in Stavanger, is about pounds 250m. The fleet will number 156 helicopters.
The main business of both companies is support for exploration and production operations in the offshore gas and oil industries.
Business in the North Sea is thought to have been under pressure, although Bond has expanded elsewhere. Last year it bought Lloyd Helicopters, the largest operator in Australia and South-east Asia, for about pounds 30m.
Helikopter is buying an initial stake of up to 49 per cent from minority shareholders and 3i, the investment group which has held 30 per cent of Bond for 20 years. Bond's founding chief executive, Stephen Bond, the chairman, Keith Jones, and other managers control the remaining 51 per cent.
The businesses will operate autonomously for about three years, after which they will be integrated with Mr Bond, his brother Peter Bond, and executive directors of Bond Helicopters collectively holding the largest stake in the enlarged group.
Stephen Bond said: 'This new alliance is a major development within the world helicopter industry. It is a sensible development to meet a new market situation which will be created in the North Sea in 1997, when the European helicopter market will be deregulated.'