OMG. Fayetteville to Dulles DC8 overwing. The STENCH from the ventilation system caused ALL the passengers to choke and gag. It smelled of OVERWHELMING BO, vomit and bits of dust. Worst of all the Stewardess explained it away as 'propwash. HOGWASH! I have flow for 50 years prop planes, jets etc. I have NEVER smelled such a STENCH in my life! This was NOT propwash. This was Air Filters which hadn't been cleaned...EVER. A Ventilation system that had been cleaned EVER. IT was BEYOND disgusting! Between 'charging' for bags and 'charging' for seats United has ALOT of NERVE to charge over $350.00 for a seat on this plane. Nevermind the midcabin ceiling panels nearly rattled loose. On landing, I was convinced they would shake free and land on my head. It's called MAINTENANCE people! Do SOME.