def aggregation(item1, item2):
    """
    For an (airport, counters) item, perform summary aggregations.
    """
    count1, total1, squares1, min1, max1 = item1
    count2, total2, squares2, min2, max2 = item2

    minimum = min((min1, min2))
    maximum = max((max1, max2))
    count   = count1 + count2
    total   = total1 + total2
    squares = squares1 + squares2

    return (count, total, squares, minimum, maximum)