Airflow 3 Issue with Elasticsearch 9

[sfritzke-mtu]

I cannot create an Elasticsearch index in Airflow like this:
from elasticsearch import Elasticsearch

@task
def index_files_in_elasticsearch(bucket_prod: str, prefix: str):
   es = Elasticsearch("http://elasticsearch:9200")
   if not es.indices.exists(index="my_index"):
       es.indices.create(index="my_index")  

When I run the dag I get the error message: ConnectionError: Connection error caused by: NameResolutionError <urllib3.connection.HTTPConnection object at 0x6ffc5c0993d0>: Failed to resolve 'elasticsearch'.

Airflow and Elasticserarch running on docker container.
When I execute the python code into the airflow container, I can create the index in Elasticsearch without problems.

Does anyone have any idea what the problem could be?