On @BBCr4today , in the context of Flybe, it is suggested that a reduction of Air Passenger Duty on all domestic flights would avoid State aid rules.
This is almost certainly incorrect. See the Irish APD case, when the Commission held that a lower rate of APD on flights of less than 300km, was selective and therefore State aid (eur-lex.europa.eu/legal-content/…). Analysis starts at (41).
That finding was upheld by the General Court (there was an appeal on other points to the ECJ).
(There would be no objection to a reduction in *all* APD: it is the reduction of APD on some flights eg domestic flights that is problematic.)
NB too that @Andrew_Adonis was right to point out that subsidies for particular routes to remote airports eg Newquay - public service obligations - are entirely possible within the State aid rules.
And see also this important point.
