Generally, Big data ETL jobs include data migration jobs such as getting data from mysql or any relational database, perform some transformations on it and then moving the data to Hadoop tables such as Hive.
Airflow provides sqoop operators, spark operators, and hive operators, so Airflow can be used to invoke any of the Big data tasks and Airflow can also sequence and monitor the jobs. In this way, Airflow is useful in Big data ETL jobs.