Fares for flights within Switzerland seem very expensive indeed, even for dates months ahead and during the week. For example, a one-way fare on Swiss from Zurich to Geneva in September would be 323 CHF. The return fare is less, but still a lot of money. There is clearly quite a lot of demand between the two cities, evidenced by Swiss operating a number of flights every day.
The high to very high fares and the number of flights by Swiss lead me to believe that a no-frills, low-cost airline could perhaps do quite well in this market, by, for example, operating two 48-seat ATR-42s (one based at Zurich, the other Geneva) and one operating 6 rotations from Zurich to Geneva and the other 6 from Geneva to Zurich per day (perhaps less at the weekend), giving a total of 12 daily flights between Zurich and Geneva and Geneva and Zurich every day (again, perhaps less on the weekend). A total of 576 passengers could be carried every day between Zurich and Geneva and vice-versa. Fares would be priced on a one-way basis and would reflect the demand (so weekends and peak flights would be more expensive than off-peak mid-week flights) and number of current bookings (so essentially the earlier you book, the cheaper the ticket). The turnaround time would be 25 minutes. What do you think? It’d bring low fares and high frequency to those travelling on the Zurich-Geneva-Zurich route.