A Texas-based firm is to take over the operation of the UK's search and rescue helicopter service that has been mainly carried out by the RAF and Royal Navy for more than half a century.

Bristow, a leading provider of helicopter services to the offshore energy industry, has won a £1.6bn contract to provide SAR (search and rescue) from 2016.

The privatisation of the service is controversial with search-and-rescue experts, doctors, workers in the maritime industry, and people who have been rescued all expressing concerns in the runup to Tuesday's announcement.

Fears have been raised that a commercial service will have a different ethos to the one provided by military crew and staff.

There are also deep worries that plans to cut two of the 12 search-and-rescue bases, including Portland, dotted around Britain's coastline will leave some areas exposed, particularly in the English Channel.

The future of current service personnel, including Prince William, is unclear. Many are expected to apply to join the new service but there are concerns jobs could be lost.

However, the government has argued that it needs to act because the famous and much-loved Sea King helicopter fleet is approaching the end of its useful life.

The government argues that faster and more modern helicopters will be able to provide a better service than the current one. At the moment the RAF and navy operate eight bases around the UK while four are a civilian service run by the Maritime and Coastguard Agency.

But there will be anguish in some places famous for search and rescue, including RNAS Culdrose in Cornwall and RAF Valley in north Wales, where Prince William is based. The new service will be run from civilian sites nearby instead of from military bases.

The transport secretary, Patrick McLoughlin, said: "Our search and rescue helicopter service plays a crucial role, saving lives and providing assistance to people in distress on both land and on sea.

"With 24 years of experience providing search and rescue helicopter services in the UK, the public can have great confidence in Bristow and their ability to deliver a first class service with state of the art helicopters."

According to the transport department, under the new contract, 22 "state-of-the-art helicopters will operate from 10 locations around the UK.

The department insisted the new service would be better than the current one. It said: "There will be an overall improvement in flying times to incidents of around 20% (from 23 to 19 minutes). Presently, approximately 70% of high and very high-risk areas within the UK search and rescue region are reachable by helicopter within 30 minutes. Under the new contract, approximately 85% of the same area would be reached within this timeframe."

Ten Sikorsky S92s will be based, two per site, at Stornoway and Sumburgh in Scotland and at airports in Newquay, Cornwall, Caernarfon, north Wales, and Humberside. Ten AgustaWestland AW189s will operate, two per site, from Lee-on-the-Solent in Hampshire and out of a new hangar at Prestwick airport, Glasgow, while new bases for it will be established at airports at St Athan, south Wales, Inverness, in the Scottish Highlands, and Manston in Kent.

The department added: "Following 70 years of outstanding service from the RAF and RN search and rescue squadrons, military involvement in search and rescue in the UK is to cease, and with the Sea King helicopter nearing its 40th year of operations, the time has come to change the way the service is provided and the aircraft used.

"Contracted search and rescue services have operated alongside the RAF and RN since 1983 with great success, and contracted search and rescue crews have won numerous awards."

It said the contract would be managed by the Maritime and Coastguard Agency in the same way as the existing contract that operates the coastguard helicopter bases on the south coast and on the Western and Shetland Isles.

Half of the new fleet will be built in Yeovil and the contract will have a significant impact on the UK supply chain, providing and sustaining jobs and apprenticeships.

Competition for the contract has been keen.

Bristow already operates search-and-rescue operations in the UK and also in the Netherlands, Norway, Trinidad, Australia, Russia, Brazil and Canada.

Headquartered in Houston, it was the first civilian helicopter service to operate in the North Sea and remains one of the main service providers to the oil and gas industry, including search and rescue operations.

It has flown more than 44,000 operational hours in the UK, conducted more than 15,000 missions during which more than 7,000 people have been rescued.

Mike Imlach, Bristow Helicopters Ltd's managing director, said: "We will be introducing new, hi-tech helicopters to the UK, equipped with the latest search and rescue technology, resulting in unprecedented levels and quality of SAR coverage across the country. The existing expertise and local SAR knowledge is immensely valuable and we will ensure that this is not lost."

Last year, the department for transport awarded Bristow Helicopters Ltd a "gap" contract to provide search-and-rescue services with the British coastguard agency ahead of the start of the new wholly privatised service.

Through a training arm it also provides helicopter training to UK military pilots and crewmen before they move to operational squadrons.