British Airways parent IAG on Friday presented a formal offer for Irish carrier Aer Lingus worth 1.4 billion euros ($1.6 billion).
IAG has offered 2.55 euros per share, matching an earlier informal bid.
"The board of IAG is pleased to announce that the offer document containing the full terms of, and conditions to, the offer and the procedures for acceptance is being posted to Aer Lingus shareholders today," said a statement.
IAG has acted after British regulators ruled that no-frills carrier Ryanair must cut its near 30 percent stake in of Aer Lingus to just five percent on grounds of unfair competition -- a decision that Ryanair is appealing.
The Irish government has announced it would sell its 25.1 percent stake in the former flag carrier Aer Lingus to IAG, which owns also Spain's Iberia.