CDG - Transfer to flight on another airline

I've been in similar situations "gambled" leaving at least 3 hours to connect on the separate flight
You never know if the Boston to Paris will be delayed causing you to miss the separate flight.
But it is easier to stomach if you get a cheap ticket on Easy jet or pay for one that you can cancel and get a refund once you know you won't make it.

I would roll dice and try to catch the 10:45 am to Venice on Easy Jet for $58 one way ; but only with a carry on bag that met their requirements as cabin baggage.

Air France and Delta are almost one airline on trans-Atlantic flights. If you had telephoned Delta you probably could have been booked straight through to Italy, maybe paying for the shortfall in points. If you buy a separate Air France ticket you may be able to check your luggage straight through. If you go with cheapo easyJet you will have to do all the formal entrance requirements for France, and then go to the check-in desk with your luggage for easyJet to handle their priorities. Lots more time. And be sure to read easyJet's very strict luggage limits on its website, not the same as the other carriers. They are a fine value-for-money carrier but they do not allow the same privileges as Delta/Air France.

Whatever you choose for CDG-Italy, book one way tickets. That way if you miss the connection on your transfer at CDG you loose only the CDG-Italy ticket, not the entire roundtrip.

If I were to attempt this I would give myself not less than 4 hours. Sitting around bored waiting for a flight is, to me, better than booking a new flight because I missed my connection/transfer

I've done this several times - most recently this last May when I flew into Madrid using miles and connected to a Iberia flight to Lisbon that I'd bought on my own. I was due to arrive at 6:30a and depart at 8:50a, so 2:20 to make the connection, all in the same terminal in Madrid (T4). I had carry-ons only, though Iberia did force me to check one of them. It turned out the flight into Madrid landed 30 min early so I had more than enough time to spare, though of course it could have been an hour late. I think I still would have made it quite easily.

Yes, there is always a risk that you'll be delayed and miss your connection, and the possible delays vary by airline, airport, change of terminal, etc. The first question to ask is: what are the consequences if I miss the connection? Sometimes the consequences would be severe - there may not be a good direct flight at all that same day to my destination. Or it could be an expensive last-minute ticket. Or you might have to wait til the next day. In the case of my Madrid connection above, the risk was pretty manageable: there are many daily direct flights between Madrid and Lisbon, and even the last-minute fares were not 500 euros. I guessed I would have gotten one for under 200 euros if need be.

I have taken this risk at least five times and never lost - so far. Yes, some day the odds will catch up with me, but I figure I'll average the one-time cost over all of the times I made it - and minimized my layover, not wasting extra hours at the layover airport, which would have been safer. Sometimes trip delay insurance will cover some or all of the delay costs as well.

For Paris to Venice? I believe there are plenty of direct flights a day there too. Even a last-minute fare may not be that expensive; you can guess by checking tomorrow's fares today. You could also book an "insurance" fare if you like - by booking a second, later ticket, if you can say find one say on easyJet 6-8 hours later. Then it may ease your mind that if you miss the first one, you'll probably make the next one. (Sometimes these cheap flights are super cheap.) I've been content to take the risk of the step last-minute fare though.

I'd just note that Madrid is a more manageable airport than CDG.

Especially if you buy an EasyJet ticket for your onward, you'll be arriving in and departing from different terminals,.so you have to take that into account too.

I wouldn't try this with anything less than four hours between arriving and departing flights, and then pray pray pray your trans-atlantic flight isn't delayed.

But it is easier to stomach if you get a cheap ticket on Easy jet or pay for one that you can cancel and get a refund once you know you won't make it.

Of course it's one thing to lose the €58 euros or whatever you paid for the flight. It's another to pay whatever you'll have to shell out on the day to buy a same-day ticket on to your final destination (times however many in your party).

EasyJet does not sell refundable tickets by the way. You can get back the taxes paid if you cancel ahead of departure but that is it. That presumed that you're somewhere with data connection before the departure of your to-be-missed flight.

Thanks to all those who responded. Looks like the consensus is four hours. The flight from Boston is scheduled to arrive at 8:15 AM - Terminal E I will probably book an Air France flight to Venice leaving at 12:50 PM from Terminal F.

Background: I used the pay with miles option on my Delta AMEX card since I did not have enough miles to pay for the flights to Italy. The pay with miles option can only be used on a Delta branded flight. In other words, if any part of the flight is on a partner airline (e.g. Air France, KLM, Alitalia) this option is not available. Finally, I was looking for ways to use up the miles on the AMEX card since I am no longer interested in having a mileage reward card.