Between July 27th and August 9th, flights will be diverted to the Pyrenean airport, which is located 40 km away from Pau.
The diversion will allow for Pau's landing system to be upgraded, something that will enable more flights to land safely during adverse weather conditions.
Ryanair's Stephen McNamara said the diversion will "minimise the disruption" for Pau-bound passengers.
"Ryanair will contact all affected passengers via email to inform them of the amendments to their itinerary," he assured.
"These essential upgrade works will benefit all passengers in the long-term and will help to ensure that Ryanair passengers suffer fewer adverse weather related disruptions on flights to/from Pau."
Lourdes Airport currently has two scheduled destinations, a Ryanair flight to London Stansted and an Air France flight to Paris.
Ryanair will open its 32nd base in Pescara in July, basing four new flights at the Italian airport.