Via Air France, I will leave Paris and arrive at LHR with 1 sm carry on and 1 checked in bag. I will then have 3 hrs until my British Airways flight back to the US. Is a 3 hr connection time enough?

It sounds like you are not changing airports, you will have a 3 hour layover at LHR, is that correct? If that's the case, then 3 hours will be more than enough time as long as your bags are checked all the way through.

Your posts are getting very confusing. If you are flying from California to Paris, why are you stopping in London and changing airlines both ways? Can't you get a direct flight from California to Paris and return?

I'm sorry about the confusion, here are details. BA from San Francisco to LHR, 3 hr layover and then separate final leg with BA from LHR to Paris. I don't understand it but by chopping the flight into two separate segments with separate ticketing, the savings was almost $500 vs straight through from SF to Paris. Unfortunately, BA says that with separate tickets bags must be claimed and then reprocessed.

Let me get this straight. You're flying:

SFO-LHR BA
LHR-CDG BA

(3 hour transit, 2 seperate tickets)

And then,

CDG-LHR AF
LHR-SFO BA

(3 hour transit again, 2 seperate tickets)

Is that correct?

Anyways, here's the deal.

<b>On your outbound</b>, BA always say they will not transfer bags to another carrier, but it's unclear if they'll transfer bags to themselves if it's on two tickets. It depends on the check-in agent at SFO. Be nice but firm when you check-in to get them to tag your bags all the way to CDG. [And if they say yes, see if they can issue you your boarding pass too.]

If they do this, then you don't need to go through immigration or customs. If not, then you need to reclaim bags and check-in again for the LHR-CDG flight.

<b>On your return trip</b>, AF should have no problem tagging your bags all the way to SFO as long as you show them your BA itinerary. You therefore won't need to go through immigration/customs on your return trip.

3 hours is adequate for the stuff you're trying to do.

This might be worth the aggravation if you were required to use BA with a free award ticket. But you posted prices on another thread and they didn't sound all that great to me. Is there some reason you have to do this with BA instead of looking for another flight with any other airline that does nonstop from SF to Paris? You also mention you aren't going until April? It doesn't sound like the most pleasant way to start that anniversary trip.

I think the website for pricing flights is www.kayak.com, you can play around on that site to see if infact you're getting a good deal with 2 separate tickets.