Why 350 for Tu154?
Airship,
The answer to your question is on page 38 of the report:
"The control strip for the TU154M shows the intended routing NEGRA-Trasadingen (TRA) – BENOT. The estimated times of passing the listed waypoints were indicated with 21:36 hrs,
21:42 hrs and 21:51 hrs. Following the passing of Trasadingen VOR (TRA) a descent to FL350 was planned because the AIP Switzerland states that odd level numbers are to be used for the
intended flight route."