An example is Ryanair and Wizz Air operations the Bulgarian Black Sea coast. Burgas and Varna are 130km apart, have similarly sized local catchment areas and passenger demographics (but with Burgas generating double Varna’s peak summer inbound tourism), and are run by the same operator - Fraport Twin Star.
Wizz Air launched a one aircraft Varna base in July 2017 with a sensible set of routes: Dortmund, Eindhoven, Larnaca, Bergamo, Memmingen and Tel Aviv, alongside Luton which was previously operated. This was supported by a heavy investment in local marketing in the local media, billboards, Bulgarian speaking crew, and an attempt to appeal to the market.
Ryanair launched a one aircraft Burgas base in March 2018 with a somewhat eclectic set of routes consisting of Bratislava, Dusseldorf, Hahn, Krakow, Kaunas, Memmingen, Bergamo, Riga, Rzeszow, Tel Aviv, Warsaw Modlin. Milan, Tel Aviv and the German routes made sense, but no one really believed the flights to Poland, Latvia and Lithuania could be sustained year around. Ryanair relied on Fraport marketing support to put up a few billboards around Burgas but not much else.
The Ryanair base was quietly closed in October 2018. Meanwhile, Wizz Air has added a second aircraft to its Varna base with additional frequencies to Memmingen/Luton and a few new destinations Beauvais, Berlin, Cologne, Copenhagen, Hamburg, and Liverpool.