There are several synonyms for the phrase "was in operation". Some of them include "functioning", "working", "operating", "running", "in use", "active", "operational", "in motion", and "alive". All of these synonyms can be used to describe something that is currently functioning or being utilized in some way. For example, a factory that is currently producing goods could be described as "in operation", "functioning", or "operational". Similarly, a machine that is currently running could be described as "working", "in motion", or "alive". The choice of synonym can depend on the context and the specific meaning that is being conveyed.