The K691-1172A Boeing Airplane 2-car Set came out in late 2004 and was a limited edition sponsored by the Pacific NW Division of TCA. The project was spearheaded by Richard Flinchbaugh, the PNW TCA division president at the time. As I recall, Dick designed the car, worked the project with K-Line, and arranged permission from Boeing to use their trademarks on it. This car is a model of BN/BNSF cars used to transport Boeing 737 fuselages built in Wichita, KS to final assembly in Renton, WA. It is not 1/48 scale, however; it was sized down to accomodate Lionel O gauge operation. (I'm not sure what the actual scale is...maybe closer to HO ?? A real 737-700 is 105 ft, 7 inches long which would equate to 26.4 inches in O scale... )
The K691-1152 Boeing Airplane Parts Car was done the following year by PNW TCA, again managed by Dick Flinchbaugh. It is also similar to a BN prototype.
As you have probably noticed, these cars have recently been going for very high prices on ebay. I'm getting ready to list mine.....