Transport between Paris airports for connecting flight

First, is this truly a connecting flight on a ticket issued by the same airline and directly by the airline, or is it from a third-party vendor? If it's an itinerary dug up by Orbits, Expedia, Cheapoair or another third-party vendor, these will ultimately be separate tickets. Why is this important? If Air France or Icelandair, for example, has issued this itinerary on one ticket, and you miss the connection, you'll be protected. The airline will put you on a later flight, maybe the same day, maybe a few days later. If this is one of those 3rd-party itineraries, and you miss the flight, you'll have to deal with the 3rd-party, and good luck with that. You risk being stuck in a tug-of-war between the airline and the 3rd-party with neither wanting to assume costs and responsibility.

So to answer your question, you have essentially two ways. First the RER B which you can learn about here: https://parisbytrain.com/. You need to be aware of your luggage and surroundings at all times on the RER, go up and down stairs or escalators with your belongings. This is the most heavily used RER line, way overburdened, so it does have daily breakdowns and delays. At some point at some station, you transfer to a Orly shuttle line called Orlyval. Since the RER B brances into two lines south of Paris, you need to be sure you are on the correct line to catch the Orlyval.
Second, the Air France bus: http://www.lebusdirect.com/en/
You climb on the coach, put your luggage in a compartment below the bus, and let them drive while you read, snooze, etc. The last time we used it, traffic was such that the bus ride took two hours.

And those two hours in traffic is why you don't want to take a taxi. It would not be a fixed price. And Uber cannot pick up at the airport.

So, if you have another scenario available, you should explore it. If not, allow yourself a lot of time between the airports, or even spend the night in Paris and fly out the next day.

Thank you, Bets. The flights I am looking at are through Air France. There just does not seem to be enough time between flights to connect. Flying Chicago to Marseilles and found best price through Air France, but it seems the stress induced by making the connecting flight is not worth the savings. Flying out the next day means added expense with lodging, so... Looks like we will have to bite the bullet with cost of flight for the convenience and lack of stress. Thank you again for the information.

Yes, it's really a trade-off. Even connecting within CDG, allow plenty of time. Good news is AF will put you on the next available flight if you miss the connection. There are AF flights to Marseille from CDG.

You might also look at connecting to Marseilles from CDG using the TGV. If you land at 11:05, you can make the 13:58 TGV to Marseilles by 17:46. Get a flexible ticket in case you are late. 121 EUR per person.

Thank you, Sam.

Give yourself plenty of time. It takes me a full hour to get from my plane to RER, buy a ticket from a machine and be rolling out of CDG - that's having entered Schengen in Iceland and no checked bag. Plan on longer if you need immigration and/or checked bags. Another 45 minutes to get downtown on RER, then 30-40 minutes to get to Orly. As I recall Air France flies out of the first terminal you get to, so that saves a few minutes. Be sure to buy a ticket that includes Orlyval, I've heard the transfer from RER to Orly by itself is expensive.

As was stated above, RER B forks on both ends of the run, some trains don't go to either CDG or Orly. If you board at CDG, you don't have to worry about that end, but you do want a train that takes you to the Orlyval connection. If it's not the correct train, I'd still ride it as long as you can. Hop off after you get through downtown, to avoid the biggest crowds, there's at least a few stops before it forks, then get on the next one that takes you to the Orly connection.

The flights I am looking at are through Air France. There just does
not seem to be enough time between flights to connect. Flying Chicago
to Marseilles and found best price through Air France, but it seems
the stress induced by making the connecting flight is not worth the
savings. Flying out the next day means added expense with lodging,
so... Looks like we will have to bite the bullet with cost of flight
for the convenience and lack of stress. Thank you again for the
information.

I'm confused. Is this one itinerary on Air France in which you have to transfer to ORY for the flight to Marseilles? Or are these 2 separate Air France flights? It's hard to believe that this trip to Marseilles from Chicago is on one ticket as opposed to 2 separate tickets on 2 separate itineraries with Air France.

I know that Air France offers routes on one ticket that require the traveler to connect in Paris from CDG to Orly. I never take those because I figure with my luck, I'll miss the connection. In any event because the traveler has to pick up luggage and transfer it and Air France does not assist with the connection, I would not do this unless I had at least a 5-hour window to make the trip.

And in a five hour window just to transfer, you could be at Gare de Lyon and well on your way to Marseille. The TGV is three hours, and prices start very low when tickets become available three months in advance.

For this route, I’d just take a TGV from CDG to Marseille.

Continental, the flights I was looking at are through Air France in which we fly into Paris, but have to transfer to Orly for the connecting flight. It's all on the same ticket.

Continental, the flights I was looking at are through Air France in which we fly into Paris, but have to transfer to Orly for the connecting flight to Marseille. It's all on the same ticket.

Jan, I was bit surprised that AF is not offering a TGV Air ticket which is a transfer at CDG to the TGV and if your flight is delayed they put you on the next train for this route so I checked and sadly Marseille is not one of the stations in that program. For your trip, direct trains depart from CDG to Marseilles just about every two hours and the trip takes less than 4 hours and non-exchangeable, non-refundable tickets bought 3 months ahead of time cost about 25€. Something to consider, I think.
For others who might read this thread looking to go to certain cities, you may want to take a look at TGV Air service: https://www.airfrance.us/US/en/common/resainfovol/avion_train/reservation_avion_train_tgvair_airfrance.htm.

SNCF (French railroad) has a station at CDG - just go down the escalator and you're on the platform - jump on the TGV and you're on your way.

Tickets are available 90 days before departure and are cheaper when purchased in advance.

Works very well and the trains are nice -