Carsten Thomassen asked in 1976 whether there exists a planar hypohamiltonian oriented graph. We answer his question by presenting an infinite family of planar hypohamiltonian oriented graphs, the smallest of which has order 9. A computer search showed that 9 is the smallest possible order of a hypohamiltonian oriented graph.
['Susan A. van Aardt', 'Alewyn P. Burger', 'Marietjie Frick']
An Infinite Family of Planar Hypohamiltonian Oriented Graphs