Use the Fly.io flyctl CLI for deploying and operating apps on Fly.io: deploys (local or remote builder), viewing status/logs, SSH/console, secrets/config, scaling, machines, volumes, and Fly Postgres (create/attach/manage databases). Use when asked to deploy to Fly.io, debug fly deploy/build/runtime failures, set up GitHub Actions deploys/previews, or safely manage Fly apps and Postgres.