How did theseus solve the problem of not changing the sail on his ship?

Theseus solved the problem of not changing the sail on his ship by instructing his crew to change the sail from black to white upon their safe return from Crete. He believed that this visual signal would inform his father, Aegeus, that he had survived and defeated the Minotaur. However, in a tragic turn of events, Theseus forgot to change the sail, leading Aegeus to mistakenly believe his son had died, resulting in Aegeus's despair and subsequent death.