That's worth checking into. I was only going by what their web site says about baggage policies:

Non-motorized bicycles, including Bike Friday and Co-Pilot, will be accepted in substitution of a free piece of checked baggage at no additional charge provided the bicycle is properly packaged and the box containing the bicycle fits within the 62-inch sizing limit and weighs 50 pounds or less. (Maximum weight is 50 pounds and maximum size is 62 inches (length + width + height per checked piece of luggage.) The handlebars, kickstand, and pedals must be removed and placed inside the box. A $50.00 each-way charge applies to bicycles that don't meet the above criteria. Bicycles packaged in a cardboard box or soft-sided case will be transported as a conditionally accepted item.

I took that to mean a bike with S&S couplers that will fit into a 62-inch box (length + width + height) could fly for free as one of your checked bags. All other bikes fly for $50 in a suitable cardboard box or soft-sided case. I interpreted that to mean a standard size bike box. They might very well have a different interpretation.

Since I'm only flying one-way, I'll check with the airline desk at my departure city well in advance. Thanks for the warning.