Ryanair faces an “in-depth” European Commission probe into whether it received illegal state-aid in return for promoting Montpellier and the surrounding area on its website.
Commissioner Margrethe Vestager, in charge of competition policy, said: “Competition in air transport is of fundamental importance for consumers, growth and jobs.
“We will investigate whether regional and local authorities in France granted an undue economic advantage to Ryanair over its competitors, potentially harming other European airlines and having spill-over effects to other European regions.”
Montpellier airport is located in the French region of Occitanie and is one of the 20 largest in the country, handling 1.9 million passengers in 2017.
The complaint concerns marketing agreements between the Association for the Promotion of Touristic and Economic Flows and Ryanair.
The unnamed complainant alleged that the agreements amounted to illegal state aid in favour of Ryanair.
The Commission has concluded a number of cases in the last few years regarding aid to airlines aimed at attracting or maintaining capacity at certain airports, finding that they were not in line with state aid rules.
These include airports at Nimes, Pau and Angouleme in France, three in Sardinia, two in Germany and one in Austria.