The Roman plan was to sail south from Messana round Cape Pachyrus and head west to Cape Ecnomus where they would rendezvous with Roman land forces encamped there. Then the fleet would proceed on to Africa. If the Punic fleet was encountered, the Romans planned to drive it out of their way.
The Carthaginians through their spy network were able to follow the Roman advance and arrange the battle on their schedule. Moreover the Carthaginians had spied on Roman maneuvers where the attack formation was rehearsed.