Let q be an odd prime power such that q is a power of 5 or q≡±1 (mod 10). In this case, the projective plane PG(2,q) admits a collineation group G isomorphic to the alternating group A5. Transitive G‐invariant 30‐arcs are shown to exist for every q≥41. The completeness is also investigated, and complete 30‐arcs are found for q=109,121,125. Surprisingly, they are the smallest known complete arcs in the planes PG(2,109),PG(2,121), and PG(2,125). Moreover, computational results are presented for the cases G≅A4 and G≅S4. New upper bounds on the size of the smallest complete arc are obtained for q=67,97,137,139,151.