Newquay will be the sole search-and-rescue helicopter base on the Westcountry coast after a Texas-based firm took control of the vital emergency service.
MPs across the region were last night alarmed over offshore safety as a privatisation deal ended 70 years of a service run by the RAF and Royal Navy squadrons.
The £1.6 billion contract will see helicopters withdrawn from RNAS Culdrose near Helston, Cornwall, and RMB Chivenor near Braunton, North Devon.
The civilian search-and-rescue helicopter based at Portland, Dorset, has also been ditched.
In their place, Newquay airport has been chosen as one of ten locations around the UK where 22 state-of-the-art helicopters will operate from under the ownership of US-headquartered Bristow Helicopters.
It also spells the end of the use of iconic grey and yellow Sea King helicopters in search-and-rescue work flown by Prince William, the Duke of Cambridge, among others.
Andrew George, Liberal Democrat MP for St Ives, whose constituency includes Culdrose, said: "I have concerns that both the operational capacity of Culdrose and its capacity to attend many incidents in the far reaches of the Western Approaches will not receive the same response from Newquay."
South Dorset Tory MP Richard Drax, whose constituency includes Portland, said: "It's my view and the view of many others that the loss of the helicopter will lead to more deaths."
The Department for Transport said that under the new contract helicopters will be able to reach a larger area of the UK within one hour of take-off than is currently possible.
Half of the new fleet will be built at the AgustaWestland factory in Yeovil, Somerset, and the contract will have a significant impact on jobs.
Two Sikorsky S92s will be based at Newquay. A spokesman added cover for the north coast of Devon would now be provided from St Athan in South Wales, where two AgustaWestland AW189s will be based.
The handover, the result of Labour's push for privatisation in 2006, will begin in 2015 and be fully up-and-running in 2017.
The end of Royal Navy 771 Squadron at Culdrose and RAF 22 Squadron at Chivenor are unlikely to have a huge impact on the viability of either large base.
And the 16-personnel strong squadrons will get the opportunity to transfer to Bristow Helicopters or redeploy in the military.
Bristow Helicopters is the third company to open a base at Newquay airport's "Aerohub" since its launch last year, and will create more than 30 jobs.
Stephen Gilbert, Liberal Democrat MP for St Austell and Newquay, said: "This is a real vote of confidence in Newquay airport.
"The aim is to provide a world class search-and-rescue capability with the most modern of equipment that will improve coverage around British waters and make those who use the sea safer."
Al Titterington, managing director of Newquay Cornwall Airport, said: "The new contract will bring additional income to the airport which will help ensure that the subsidy provided by Cornwall Council continues to reduce year on year, as well as supporting job creation at Newquay and safeguarding jobs in Cornwall."
The company said the ten bases would be strategically situated near areas of high incident rates. All bases will be operational 24 hours a day.
The new contract will 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.
Based on historic incident data, it is estimated there will be an overall improvement in flying times to incidents from 23 to 19 minutes.
Transport Secretary Patrick McLoughlin said: "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."
Bristow Helicopters said the "technologically advanced" helicopters would be operated by experienced crews with "world-class" skills. It expects to create around 350 jobs to support the contract.
Mike Imlach, the firm's managing director, said: "We will introduce new helicopters to the UK equipped with the latest search-and-rescue technology that will deliver unprecedented levels and quality of search-and-rescue coverage across the country."
Meanwhile, it promised the helicopters would be more advanced than the Sea King model they will replace, with night vision, mission management and increased on-board medical capabilities.