The two main airports of Paris, Charles de Gaulle Airport (CDG) and Orly, are on opposite sides of the city. Paris Charles de Gaulle Airport (CDG) is in the north, Orly the south. Both require a bus, train or shuttle transfer through or around Paris.
The three main options to make this journey are Le Bus Direct buses that run non-stop between the two airports, Line B of the RER Paris trains that go through Paris centre and private vehicle or taxi.
Le Bus Direct runs a dedicated airport service running non-stop around the periphery of Paris.
The service runs 7 days a week leaving both Paris Orly and Paris Charles de Gaulle (CDG) airports every 30 minutes. Journey time is scheduled at 90 minutes, though at peak time and during commute hours there can be severe road congestion delays on the route.
Buses run from about 6am to 10pm at 20-30 minute intervals from Paris Charles de Gaulle Airport (CDG) and from about 6.30am to 10pm at 20-30 minute intervals from Orly.
Adult fare between CDG and Orly Airports: €22.00 (Return fare: €37.00) Child fares up to 40% off for 4-11 year olds and children under 4 go free. (Last checked Feb 2020.)
The RER train service from CDG Airport goes through the centre of Paris and out the other side and continues to within a few miles of Paris Orly Airport.
At Antony Station a small shuttle train runs a dedicated service to Paris Orly. Both service all terminals in each airport.
If using this service be careful on Line B of the RER where there are several branches to the line. Make sure the train you board goes to Paris Charles de Gaulle Airport (CDG) or Antony.
Scheduled journey times are more reliable than the Le Bus Direct as there is no road congestion to contend with.
You should do the journey comfortably in about an hour. The service runs between 6am and 11pm.
The ultimate in convenience for transferring between Paris Charles de Gaulle Airport (CDG) and Orly is of course a private vehicle with driver, door to door with meet and greet at the airport.
Journeys are prone to traffic congestion, but the approximate journey time is 40-60 minutes.
There is a flat fare system with a published standard tariff between Paris Charles de Gaulle Airport (CDG) and Orly.
The aim is to make the whole operation as simple and as transparent as possible.