The passengers say they arrived on time for the flight which took off at 3:10 p.m. on Nov. 24, The Connexion newspaper reported.
The airline initially blamed the incident on passengers arriving late but later mentioned "security delays."
Some affected passengers said issues such as repeated requests to remove shoes and time wasting during security checks prevented them from showing up at the boarding gate on time.
Many of these travelers were reported to carry prohibited items in their luggage such as perfumes over 100 ml.
A representative of Ryanair said that all passengers who missed the flight "were assisted with booking on the next available flight from Carcassonne to Brussels."
Last week, a plane of Turkish-German airline SunExpress took off from Paris to Izmir in Turkey, leaving 30 passengers at the airport.