It used to be that bicycles flew on international flights for free. Not so anymore—most airlines have begun to crack down. I've provided our own experience with Air France below in case you are contemplating such a trip and are interested in what happened to us. 

We went from Toronto to Douala via Paris CDG (with a 2 night layover) and back again with both (a) a boxed bicycle and (b) a Dahon folding bicycle in the Dahon Airporter suitcase. Here is a summary of our experience:

• At Toronto YYZ they immediately knew that we had a bicycle in the box. They automatically made us pay $150 for it. However, since we had a 2-day layover before continuing on to Douala I asked if I'd be charged again for the 2nd leg and they provided another receipt for that portion. SO IF YOU HAVE A LAYOVER BE SURE YOU ASK FOR A RECEIPT FOR THE SECOND LEG.
• My Dahon, even though oversized and slightly overweight, was not even blinked at by the staff.
• FYI, at CDG you can store excess baggage at a place called Baggages du Monde for a daily fee (15 Euros per piece per day) since you can't check it all the way through to your final destination. They will take it off-site for storage and bring it back at the time you specify for pick-up.
• Leaving CDG for Douala, I never had to haul out my receipt for that portion: we confirmed it was a bicycle when asked and it went merrily on its way without an attempt at charging us. Ditto for the Dahon in its case.
• Leaving Douala we had stuffed my Dahon case so it was well over its weight and size limit. The airline didn't say anything. They also didn't charge for the boxed bicycle.
• Il Kim, who few from Pittsburgh, did not have to pay for her boxed bicycle either on either portion of the journey (though airport security did open her box to inspect it).

So all this to say that your experience is likely going to vary based on the airport and maybe even who is working that day!

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