The first of the Chinook Mk 3 helicopters bound for Afghanistan have arrived at a military base in Hampshire after an eight-year delay.
The two helicopters - refitted by Boeing at Boscombe Down, Wiltshire - were unveiled at RAF Odiham.
The Chinooks, bought in 1995 for £259m, could not be used because they did not meet airworthiness regulations.
Defence Secretary Bob Ainsworth said they would give an uplift in capability to support "coalition efforts".
Mr Ainsworth added: "I am delighted that the first of the Mk 3s are now joining the Chinook fleet.
"By the end of this year we expect to have all eight of these refitted aircraft in service, increasing our Chinook fleet to 46 aircraft."
Software problem
At the end of last year, he revealed the government planned to purchase 22 more Chinooks.
The Commander of Joint Helicopter Command, Rear Adm Tony Johnstone-Burt said: "These aircraft will be vital in helping us expand our ability to train our crews and to support operations.
"They really will make a difference."
When the helicopters were delivered by Boeing (which had met its contractual obligations) to the MoD in December 2001, it was discovered that the avionics' software was unable to meet UK regulations.
The entire cockpit had to be refitted to meet British requirements.
In 2004, the Committee of Public Accounts described the original purchase of the Chinooks as "one of the worst examples of equipment procurement" that it had seen.
The refitted helicopters, which are considered vital to operations in Helmand, also have extended-range fuel tanks and more powerful engines - enabling them to lift heavier weights.
The government has come under heavy pressure in recent months over the number of heavy-lift helicopters in Helmand.
Conservative leader David Cameron has previously called the shortage "a scandal".
