Businessman Denis O'Brien has spent €2.5m buying more shares in Aer Lingus.
In the past, Mr O'Brien has stated his opposition to Ryanair's attempts to take over Aer Lingus.
In a statement to the Irish Stock Exchange this afternoon, Mr O'Brien's company confirmed it had bought one million shares in Aer Lingus. He now owns 2.2% in Aer Lingus.
While his latest purchase is a relatively small one it comes at a crucial time, as it is expected that the European Commission will make a decision on whether Ryanair should be allowed take over Aer Lingus next week.
Mr O'Brien has said in the past that he wishes Aer Lingus to remain independent of Ryanair, saying he supports pilots, staff and management.
By increasing his stake even a small amount it does make buy out by Ryanair more difficult; Michael O'Leary-run Ryanair already owns a 25% of Aer Lingus.
But the anti-Ryanair camp, which is mainly made up of workers and the Government, owns more than 45% of Aer Lingus.
