Good stuff, dzierzak. Nice record keeping.

Up until 2011, all my personal packs were external frame. OK, lets be clear about this...they were Kelty's produced and purchased in the period from 1966 to 1970. From 1969 on, I have flown over 30 trips (Canada, Colorado, Nevada, Arizona, Mexico, Central and South America, and the south pacific) with my Kelty external frame never once having it stored inside something else; it was marked tagged directly as luggage, loaded onto a plane via the usual methods and the worst that happened was an end cap got lost once and the ends of the frame were beat up. I still use this backpack, btw. This is a pretty tough pack though; I'm not sure or very familiar with other external frame designs. My ultralight backpack I am far more worried about and at a minimum will put it into another piece of luggage or duffel bag to keep it safe. But the Kelty's have more damage done to them from bears than from flying. A duffel bag would only up the protection with possibly the exception of the frame ends.

Times have changed though, so I would call the carrier and talk to them about it and keep a telecon record about it if you are really fastidious. The plastic bins were pretty clever as they stacked and protected the backpacks. More and more people are using backpacks again for travel so maybe this is part of a trend and the various providers are moving to accomodate.