A relative who is a very inexperienced traveler is traveling from Atlanta to Seville. He purchased a cheap ticket online that takes him through Paris via CDG on Delta airlines with a transfer to Orly and on to Seville on Air France. He has 4 hours between arrival at CDG and departure at Orly. Is this enough time?
Probably, have him take the RER, which goes straight between the two.
He should be OK, if there are no holdups. Say an hour to get off the plane, collect luggage, go thru customs, and get to the RER station at CDG. Another 90 minutes, tops, to take the RER B-4 train through Paris and out the other side to Antony station, and onto the Orlyval shuttle train to the airport. There are two terminals at Orly, so make sure he knows which one to get off at.
4 hours should be ok, but I would warn him CDG gave me the worst airport experience of my life. Inefficient and rude clerks, only two passport agents for several hundred people coming off of several flights at once. I finally found an English speaking passenger assistance person who helped me. The staff I asked about my connecting flight gave me wrong gate information, the flight info wasn't listed at the gate and we missed our flight. He should ask several people the same info when he gets there to double check to see if he is going to the right place.
There are Air France coaches (bus) that go directly from CDG to Orly. The cost is 16 euros. Go to the Cdg or Orly websites and you should find a link to the Air France coach website.
If he chooses the Air France coach, make sure he's aware that, depending on the time of day, traffic around Paris can be paralysed. Air France recommends at least 2:15 for a transit time....which, after he gets out of CDG to the pickup point with his luggage, may not be enough time to check in at Orly.
Thanks to everyone for your replies. From what I have read, Air France coach seems to be the best option because of luggage. I think he will be in Paris on a Sunday. Is traffic as much an issue on weekends? Also, what's the worst case scenario if he misses that flight from Orly?