GET flights/_search
{
  "size": 0,
  "aggs": {
    "unique_airlines": {
      "cardinality": {
        "field": "AIRLINE"
      }
    }
  }
}

GET flights/_search
{
  "size": 0,
  "aggs": {
    "group_flights_by_airline": {
      "terms": {
        "field": "AIRLINE",
        "size": 14
      },
      "aggs": {
        "avg_flight_duration_by_airtime": {
          "avg": {
            "field": "AIR_TIME"
          }
        }
      }
    },
    "max_avg_flight_duration_by_airtime": {
      "max_bucket": {
        "buckets_path": "group_flights_by_airline>avg_flight_duration_by_airtime"
      }
    }
  }
}