Ryanair could be forced to reduce its stake in Aer Lingus, after a provisional ruling by the UK's competition watchdog.
It has found that Ryanair has influence over Aer Lingus, which could lead to a reduction in competition in flights between Ireland and the UK.
The Competition Commission said it is considering forcing Ryanair to reduce its 29% stake in Aer Lingus or sell it all.
In a statement, Ryanair has rejected the finding, calling it "bizarre and manifestly wrong".
It said it will appeal the ruling.