The European Commission (EC) is expanding its investigation into whether airports in Europe are benefiting from state aid and have agreements with airlines that violate European Union rules.

The move expands an existing review into the relationship between the airport in Charleroi, Belgium, and Ryanair, and adds new reviews linked to airports in Dortmund, Germany, and Angouleme, France.

At Charleroi, the issues are whether state aid provided to airport operator BSCA contravenes EU rules, with concerns in Brussels that the rules were not drawn up on market terms as required. Moreover, the EC wants to know if some of that aid was passed on to Ryanair.

In Germany, the EC says it is adding to its review coverage of “public guarantees granted in favour of the airport as well as a new scheme of charges, called NEO, put in place in 2009.” Brussels “has concerns that the system of airport charges operated at Dortmund could procure the airlines using the airport an undue economic advantage which their competitors do not have.”

Angouleme does not appear to reflect market terms, the EC says, adding that it “has concerns that contractual rebates and marketing arrangements concluded between the airport and Ryanair in 2008 could have procured the latter an undue economic advantage over its competitors.”

Third parties will now be given an opportunity to weigh in on the review before a formal judgment is passed.