I am a long-time dedicated Contax user and a less experienced Leica user.
Originally Posted by Woolliscroft
I would heartily counsel the purchase of the 167MT for just about any application except the one you describe. In my opinion, "reliable long term under heavy use in a high vibration environment" excludes both the R4 and the Contax 167MT. The glass for both would be fabulous, well beyond the limitations imposed by handholding on C-41 in a roaring airplane. But I would suggest a more ruggedly constructed body, such as a Nikon F3. The F3 would offer interchangeable prisms to boot. One look through a monster Nikon sports finder and you will never be the same.
Plus, the Nikon lenses are superb optically and I am not sure that they have ever been equalled mechanically. Please remember, I am not shilling for Nikon. I use Contax every day and feel that the 167MT is one of the greatest marriages of price and functionality ever achieved. I would love to see another convert to the Contax family, but want to be sure the pilot picks the best tool first and foremost.
Of course, if the idea of hanging from the window of a Cessna with a Leica or Contax around your neck is just too romantic to ignore, and practicality is not the prime directive, then just go for it!! Life is too short to sweat the small stuff!
Just my two cents. Enjoy and let us know how you make out.