The deployment by the departments of Fire and Emergency Services and Parks and Wildlife is aimed at helping the Esperance community with its bushfire preparedness during a high-risk period.
Two fixed-wing water bombers arrived in Esperance on Tuesday.
Emergency Services Minister Joe Francis said each water bomber was able to drop 3150 litres of suppressant at a time.
"The aircraft will be stationed there for five weeks to provide extra coverage while farmers are harvesting," Francis said.
Environment Minister Albert Jacob said the aerial fleet was vital in supporting firefighting efforts on the ground.
"The aerial firefighting fleet plays an important role in reducing the rate of spread in the early stages of a bushfire," Jacob said.
"The fleet also provides crucial fire mapping information to the Incident Controller on the ground, which helps with decision-making about how to best combat the fire."
Francis said the aerial fleet could not combat fires alone, and a team effort was needed when preparing for, and responding to, bushfires.
"Everyone must understand they cannot rely on water bombing aircraft saving their property this summer - we must all take responsibility and ensure we are bushfire ready."