I have a hard case which I used for my triathlon bike for travel to races... you don't want nasty surprises. Used it a couple of times for Xterra world champs too but normally I just go with a cardboard bike box in a soft bike bag for my MTB travels. I did quite a few business trips and assignments with my MTB to NY and San Jose like this, as well as domestically, and never suffered any damage.
The solid box weighed 11kg empty, whereas my current packaging is 4kg, but another reason was every time I arrived in the US the TSA morons would open the box and start moving shit around without the slightest realisation, understanding, or even concern, that it all had to go back in the same place within a few millimetres if the box was to close again. These same Stu Pitcairns also jemmied open the combo lock even though the combination was clearly written ON IT FFS! You had to close the combo lock otherwise the latch was not held. They also smashed through the key locks even though they were not locked. Total fug khans. TSA = totally stupid arseholes! They operate with total impunity too as the act authorises them to use force to open bags/items.
One time going through LAX this fat cow opened the box and was just pulling stuff all over the place. at one stage she nearly had it shut but she didn't understand the edges interlocked and had to be aligned with each other into to do so. I said "you need to align the edges." She misinterpreted me and said "lie it on the edges?" and proceeded to roll my bike box around like it was lucky draw barrel - I was nearly apoplectic. She was having a lot of trouble closing it and I said "let me" and she said I had to stand back, I realised that it could be seen as compromising the secure search she'd just done so I offered to do it nude and started to undress, I did not care I was that furious with this moronic cow. The other guys, her colleagues were simply laughing at the trouble I was having. In the end the stupid cow said "well ahhm not gonna take all day to close it" and just taped it up. I had to just bite my tongue fortunately nothing was damaged even though the box actually relied on being closed because together the interlocked edges provided structural reinforcement and stiffened the whole box. From then on I offered TSA agents and free coaching session on how to open and close my bike box before they searched it. It seemed to convince them all that they didn't need to look any further.