I am working with the following data structure

Array
(
    [0] => Array
        (
            [0] => Array
                (
                    [0] => Flight Number
                    [1] => flight_number
                )

            [1] => Array
                (
                    [0] => Array
                        (
                            [0] => Timestamp Departure
                            [1] => timestamp_departure
                        )

                    [1] => Array
                        (
                            [0] => Timestamp Arrival
                            [1] => timestamp_arrival
                        )

                )

        )

    [1] => Array
        (
            [0] => Departure City
            [1] => departure_city
        )

    [2] => Array
        (
            [0] => Arrival City
            [1] => arrival_city
        )

)


Max depth of array is: 4