Thanks. I think the 1.7 works o.k. with the 600. I use it all the time - 99% of the time like here.
I haven't carried a 600 on a plane before. I hope it fits into my case.
We have traveled with it often, Lowepro Road Runner. I think the Think Tank national is also good.
I was never happy with the use of the 1.7X except with the f2.8 lenses. Your looks good.
Make sure you can set the 70-200 on a tripod, for early morning blasts off and scenic.
I think the 1.7 works better when you are close to a small bird and want it to fill more of the frame rather than when you are far away and just want to get a shot of something the 1.4 doesn't give enough reach.