What Varadker said was based on how the EU might react to a crash-out Brexit, not what Dublin would "threaten" to do unilaterally. While Varadkar may have been mistaken in referring to overflights, the problem is much more real when it comes to flights into the UK from EU member states, including Ireland.
Ireland has more to lose than the UK from Brexit, and aviation provides a dramatic example of possible collateral damage. I looked at the Sun's despicable comments about Varadkar being an Airhead. At times I thing the appalling Trump has a point when he characterises the media as the enemy of the people. How many people in the UK are influenced by the poisonous and lying nonsense emanating from the Sun and other newspapers?