An absurd amount of bubble wrap around pretty much everything. I also cut pieces of PVC to act as spacers & support for the chainstay and front fork, two spacers each, held in place with electrical tape wrapping, hoping that will protect those parts from potential compression/crush situations. Then more bubble wrap. I once found a pedal rolling around in the main compartment which I attribute to TSA not being careful to put it back in the accessories pouch after inspection, so I’ve taken to bagging all the removable small parts in a single gallon-size Ziploc and putting that entire thing into the accessories pouch, hoping they’ll just pull the single bag, take a peek, and put it back rather than handling every part separately.
So far so good after about half a dozen flights with the bike.
The main vulnerability of that bag is to aerobars and basebars being loaded from the side and snapping, and there’s just not much you can do about that. Rotate brake levers in, make sure shifters are down if you have mechanical shifting, and remove your rear derailleur. I seriously doubt any amount of padding is going to protect your bike from anything that would get through the bag otherwise. I’ve flown with my bikes in mine probably 15-20 times now, no issues, but I have aluminum bars
I’ve flown with a 2.0 and a 3.0 aerocomfort from California to Maryland, CdA, England, Switzerland, Maui, etc and have never added extra protection. I had a rear bottle cage break once, otherwise no issues. The bag is rock solid. Put empty bottles in the cages and you should be good.
I’ve taken dozens of flights with my Scicon bag and use a few things as extra protection:
- Albopads (they were recommended on ST a few years ago. Think they’re out of business now.)
- cut sections of pipe insulation
- bubble wrap
- towels or kit stuffed between the rear fork and the bag
Like has been mentioned above, I find protecting the rear derailleur and the bar-end shifters & brakes to be the most critical. The rest doesn’t get jostled or bumped as much as those do.