Helicopter search and rescue for Caernarfon, St Athan
Helicopter search and rescue will move to Caernarfon from Anglesey and a new base will be set up at St Athan after a US-based firm won the contract to run the UK service.
The Bristow Group has won a 10-year contract from 2015.
Under the deal, 22 helicopters will operate from 10 UK locations, including Caernarfon in north Wales and St Athan in the the south.
The £1.6bn deal ends 70 years of search and rescue from the RAF and Royal Navy.
It will also mean the end of search and rescue (SAR) operations at RAF Valley on Anglesey.
Its base will be relocated to Caernarfon Airport, though the RAF base will remain at Valley. The search and rescue operation at RAF Chivenor in Devon will move to MoD St Athan in the Vale of Glamorgan.
Two helicopters will be based at both Welsh sites.
Bristow Helicopters is an Aberdeen-based company, although the corporate headquarters of the Bristow Group is in Texas. It also has offices at Redhill, Surrey, near Gatwick Airport.
The firm will replace the ageing Sea King helicopters with modern Sikorsky S-92s and AgustaWestland 189s.
Two S-92s will be based at Caernarfon and two AW189s will operate from St Athan.
The firm said its contract would create 350 new jobs across the UK but it was unable to say how many it expected in Wales.
Vale of Glamorgan MP Alun Cairns said he understood the St Athan base would mean better flying times and improved coverage of high risk areas.
Mr Cairns said the new contract would mean about 85% of high and very risk areas could be reached by helicopter within half-an-hour, compared with 70% at present.
"This follows the good news last month that the MoD base at St Athan will become the home for the Royal Signals," said Mr Cairns.
"That commitment guarantees MoD funds in the area with increased spend from soldiers through to contracts for local builders for structural projects on site. The contract for the search and rescue service will help the local supply chain, providing and sustaining skilled jobs."
Bristow Helicopters managing director Mike Imlach said he was looking forward to establishing the new base in St Athan.
He said: "We will be making significant pre-operational investment in the base as we prepare to take over the UK SAR contract in 2015.
"Bristow Helicopters Ltd is committed to sourcing our infrastructure, ongoing maintenance and supplies locally, which will create new opportunities for businesses and SMEs (small and medium-sized enterprises) in the area."
Aviation analyst Chris Yates said the two new Welsh bases would allow the service to provide extended coverage.
He told BBC Radio Wales: "Wales is doing extremely well out of it. There's some very difficult terrain right across the country, of course, and often at times people do get into difficulty.
"We've seen people rescued off Snowdonia recently and there's a whole chunk of the Irish Sea that helicopters based up in Caernarfon would operate out to in the event of a marine incident."
Anglesey MP Albert Owen described it as a "negative step".
'Step into the unknown'
He said a lot of money had been invested in making RAF Valley a centre of excellence for search and rescue, adding that the UK government was "doing this to save money - yet they are gambling with lives".
Former Plaid Cymru leader Ieuan Wyn Jones, the Welsh assembly member for the island, also criticised the decision to move a "much-valued service" from Valley.
"The sell-off is a step into the unknown in that we cannot be certain that it would provide service equal to that provided by the RAF," said Mr Jones.
"The government has not got a good record on privatising similar services and we remember that the Department of Transport itself has not got a good record, bearing in mind the mess up over rail franchising."
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."
Bristow's website says its helicopters and pilots have already rescued more than 7,000 people in the UK.
It also operates in the Netherlands, Norway, Trinidad and Tobago, Australia, Russia, Brazil and Canada.
The other current search and rescue bases are Culdrose, Wattisham, Valley, Boulmer, Portland, Lee-on-Solent, Chivenor, Leconfield, Lossiemouth and Prestwick.