BANGKOK (AP) — A fleet of drones, trucks and small planes are spraying water to try to reduce dust around Bangkok while the governor invited critics to brainstorm better ideas to improve the air quality in the Thai capital.

Unhealthy levels of air pollution forced city schools to close Wednesday for the rest of week, and the Public Health Ministry is advising against outdoor activities.

Bangkok's governor, Police Gen. Asawin Kwanmuang, said Thursday drones aren't a long-term solution but he thinks every bit of effort helps. At a morning news conference, he said critics calling the drones a meaningless stunt would otherwise criticize him for doing nothing.

Asawin invited private-sector experts and academics to share ideas, saying: "Those are knowledgeable on this issue don't give opinions to others, tell me."