Aer Lingus and the Irish government yesterday confirmed plans to list the airline on the Dublin and London stock exchanges at the end of next month.
Analysts expect the flotation - the first of an airline on the LSE since easyJet six years ago - to value the airline at up to one billion euros (£676 million).
A sale prospectus, including the price range, will be published in the second week of September.
The company is expected to kick off a European "road-show" next week to promote the shares to potential investors.
Shares will be offered to domestic and international institutions. The public in Ireland and the UK will be allowed to buy, but a minimum subscription of 10,000 euros (£6,765) will apply.
The Irish government will retain a significant minority shareholding of at least 25.1 per cent in Aer Lingus in a bid to safeguard its strategic interests, such as prized slots at Heathrow.
More than 50 per cent of the airline's issued share capital will remain in the hands of Irish shareholders following the sale, including the government, employees and private investors. It is currently 85.1 per cent Irish government-owned, with the remaining 14.9 per cent with the employees.
The partial sell-off, which has long been a hot political issue in Ireland, has been dogged by problems, including a row between management and unions over a pensions shortfall.
Unions at the airline remain opposed to the privatisation, fearing it threatens the job security of members.
Aer Lingus, which has a 3,500-strong workforce, has realigned itself as a low-cost carrier since a brush with bankruptcy in 2001.