The EU Commission has published proposed new guidelines covering State aid for new routes from Europe's regional airports.
The commission said increased competition and the emergence of low-cost carriers was prompting many airports to encourage airlines to open up new air services.
The commission said it wanted to encourage this, but also intended to ensure equality of treatment between airport operators and between companies.
It said its draft guidelines would allow greater transparency. They restrict incentives to between 30 and 50% of the additional costs over a period not exceeding five years.
The move comes in the wake of a commission decision to order Ryanair to repay about €4m to Belgium's Charleroi Airport. The commission is inviting comments from interested parties.
