To expand: I am too wordy as usual.
First of all both my wife and I overthink things because we have had bags go missing, flights canceled and we now worry about spill over from Ukraine.

We have been traveling overseas to Europe once or twice a year since 2010. Our 6 week fall trip to Greece and other places fell apart with 2 flight cancelations that could not be fixed. The Chicago to Munich flight was canceled 3 hours before it left Chicago and an hour before we were to leave Fort Wayne.

But this year the flight choices are reduced and layover time is about an hour in Chicago. If all goes as planned that should be enough. But delay getting our checked carry on can ruin it all before we leave the states.

I think the D850 is great. The trip we are taking to Montenegro, Croatia and Bosnia will have city, waterfalls, landscape; thus cover all the focal lengths from wide angle to at least 200mm. I have that covered in 3 fast lenses that with the tripod, flash extra batteries and cards, water bottle, hat and umbrella and camera bag weighs 20 pounds when hiking. The bag is 15" x 10" x 9 1/2" and should fit under the seat; and the water bottle and umbrella add height when hiking.

The tripod fits in my carryon along with a laptop, a change of clothes and with meds. When hiking I can attach the tripod to the camera bag. The carry on should fit in the overhead or under the seat if I trust the camera bag to the overhead.

The first leg of the flight is a 13 row puddle jumper with 2 seats on either side of the aisle. Under seat storage is tight and overhead limited. No way I am letting the camera equipment out of my sight and I am not too found of having the small carry on checked at the gate since the connecting time is short. The next flight is a 787-8, then a airbus A320 from munch to Dubrovnik which is fairly large and should not be a issue with carry on. Flight from DBV to FRA is a Airbus A319, FRA to ORD is a 787-9 that should have no issue with carry on. The flight from Chicago to ho is another puddle jumper and as long as I get to keep the camera there is no issue.

Thus the question becomes: do I trust that all will work out or do I take the d500 and the 18-300 or do I buy the Sony or do I just give up and use my iPhone. I know only I can answer the question; but, I value your input.