One of the unsolved
problems in the theory of projective planes is the following: Is every finite projective
plane with a transitive collineation group desarguesian? This problem is investigated
under the additional hypothesis that the group has rank 3. It is proven that if a
projective plane 𝒫 of order n > 2 has a rank 3 collineation group then 𝒫 is
nondesarguesian and either (i) n is odd and n = m4, or (ii) n is even and n = m2
with m = 0(mod4).