Ryanair has offered €2.80 in cash per share, a premium of 27 per cent over last week's flotation price and 12 per cent over Wednesday's closing price.
The offer values Aer Lingus at €1.481 billion and the Government's remaining stake in the former State airline at more than €500 million.
The employee stake will be worth €220 million or €60,000 per employee.
The offer is conditional on Ryanair getting acceptances from shareholders holding at least 50 per cent of the company.
It also has to be approved by Ryanair shareholders at an annual general meeting.
The offer is conditional on approval from the European Commission and other regulators.
Aer Lingus will be delisted if Ryanair acquires more than 75 per cent.
Aer Lingus will be a stand-alone separate company owned by Ryanair.
Ryanair will cut Aer Lingus fares and costs, but employee rights will be safeguarded in accordance with statutory requirements.
The Aer Lingus brand and the airline's Heathrow slots will be retained.
The transatlantic fleet will be upgraded and the product developed.