hi kenneth , we flew thai air recently with a 2 piece tandem without problems, they were only interested in weight not baggage size. we didnt have to pay any extra as we were within our baggage allowance. we used a large bike box ,bubble wrap and camp mats for protection . however we were well over the carry on allowance (weight wise)with our hand luggage which was in ortliebe rear panniers, but they never weigh those and they fit in the maximum dimensions given for hand luggage.you could also box up the two parts seperately to make the boxes more manageable. cheers ,calum.