What are the steps to deploy a Python web application using Flask on a Kubernetes cluster, and how can I ensure high availability and reliability?

To deploy a Flask application on Kubernetes, start by containerizing your Flask app using Docker. Then, go over the steps below:

1. Create a Docker image and push it to a container registry.
2. Write Kubernetes deployment and service manifests defining how your application should run and be accessed.
3. Deploy these manifests to your Kubernetes cluster. For high availability, configure your deployment to run multiple replicas of your Flask app.
4. Use Kubernetes liveness and readiness probes to ensure your application stays healthy.

Last but not least, consider using a Kubernetes Ingress controller to manage external access, and set up Horizontal Pod Autoscaling to handle variable load.