Bristow Helicopters Limited holds a United Kingdom Civil Aviation Authority Type A Operating Licence, it is permitted to carry passengers, cargo and mail on aircraft with 20 seats or more.After an aggressive expansion earlier in the decade, demand was cut back as crude oil prices dropped and Bristow Group's total debt stood at $1.44 billion by 30 September 2018.[7] In 1960, Bristow Helicopters chose to enter the African market via the acquisition of crop-spraying specialist Fison-Airwork, which had also operated in locations in Central America and the UK.Following an expansion programme, which included the building of new on-site accommodations for workers and their families, around thirty S-61N flights were routinely flying daily from Sumburgh, supported by round-the-clock maintenance coverage, at the peak of operations during the 1970s.[citation needed] In 1986, the company began training overseas pilots at its flying school at Redhill Aerodrome; this program ran for multiple decades, being rebranded as the Bristow Academy.[8] Starting in 1971, Bristow Helicopters began providing civilian search and rescue (SAR) services in the UK, replacing military Westland Whirlwinds with Bristow-operated Sikorsky S-55s at RAF Manston, Kent.[7] The then-unfamiliar concept of using a private company for SAR services led to a public outcry and intense lobbying efforts thus, after three years, operations were turned back over to RAF Coastal Command.Bristow reentered the UK's SAR sector in 1983 when it commenced operations on behalf of the Maritime and Coastguard Agency (MCA) from Sumburgh Airport; the company held the contract until 2007 and secured it again in June 2013.[6] The business had also developed a worldwide presence within a similar timeframe, providing its services in the North Sea, Middle East, South America, Africa, Asia, India, Bermuda, Trinidad, Australia and New Zealand.This allows Bristow to extend its range of services into new and developing oil and gas markets and helps provide a lower cost structure in some operating areas.The units were located at Portland (EGDP) and Lee-on-Solent (EGHF) on the south coast of England, at Stornoway (EGPO) in the Outer Hebrides, and at Sumburgh (EGPB) in the Shetland Isles.Southern North Sea services operate from Norwich (EGSH), Humberside (EGNJ) and Den Helder (EHKD) with its support organisation based at Redhill (EGKR).