The Government and Aer Lingus today announced details of their plans to float the airline on Dublin and London stock markets next month.
A statement from the Department of Transport and the airline said the initial public offering (IPO) will take place in late September and that ordinary share purchases will be subject to a minimum subscription of €10,000.
A flotation prospectus, including the share price range, will be published in the second week of September.
Both parties said the proceeds of the offer would be used "primarily" to finance the expansion of airline's short-haul and long-haul fleet and to finance a one-off pension contribution.
Aer Lingus plans to put the IPO cash towards a €2 billion expansion of its fleet, with emphasis on its long-haul arm, which is seen as crucial to its future.
Today's statement also confirmed that the Minister for Finance will retain a minority shareholding of at least 25.1 per cent in the company on behalf of the Government.
The Government's stake could allow it to block any sale of key assets, such as landing slots at London's Heathrow airport; employees currently own around 15 per cent.
The partial sell-off has been dogged by problems, including a row between management and unions over a pensions shortfall. The sale is also going ahead despite heightened security concerns at airports and soaring fuel prices.
Minister for Transport Martin Cullen said: "This is the right decision for the company, its employees, customers and Ireland, and it is taking place in order to give Aer Lingus both the commercial flexibility and the financial strength to succeed in what is a highly competitive global marketplace."
Aer Lingus chief executive Dermot Mannion said: "Aer Lingus has demonstrated the success and scalability of our low-cost, low fares business model across the short-haul and long-haul markets in which we operate.
"This, coupled with our continuing focus on cost control, a well-recognised brand and a strong management team and staff will enable us to capitalise on the significant profitable growth opportunities that exist for us today.
"Becoming a publicly listed company will enable us to capitalise fully on those opportunities," Mr Mannion said.
Aer Lingus has already talked to Airbus and Boeing about buying new aircraft.