A Transavia France Boeing 737-800, registration F-HTVG performing flight TO-3438 from Paris Orly (France) to Lisbon (Portugal), was enroute at FL370 about 120nm southwest of Paris Orly when the crew decided to return to Orly reporting a problem with a hydraulic system's pressure. The aircraft descended to FL280 for the return and landed safely back on Orly's runway 25 about 65 minutes after departure.
A replacement Boeing 737-800 registration F-HTVH using a maximum flight level 270 reached Lisbon with a delay of about 3 hours.
The occurrence aircraft is still on the ground in Paris about 43 hours after landing back.