I remember our Aerovias Oaxaqueñas flight in the pre-WWII DC3 that rattled & shook like nothing I had ever experienced before. There were big fires in the mountains & the National Park down to PE & there was so much smoke we couldn't see the end of the wings. We circled gaining altitude for about 30 mins and I noticed that the altimeter in the cockpit was stuck on zero (I was up front in the aisle). This is when I got nervous. Due to the fires, we couldn't see anything until we got close to the ocean. The pilots cleared the mountains & got us there through intuition & experience & it made for a memorable nail biting flight.