def filter_flash_errors(glm_data, LL_coords, UR_coords):
    """
    There appears to be dense lines of erroneous flashes around 26 N on
    10 Sep & 11 Sep from 1500-2100z. This function will remove these, but is unable
    to distinguish if a flash is genuine or erroneous.

    Parameters
    ----------
    glm_data : list of str
        List of GLM flash latitudes & longitudes
    LL_coords : tuple of str
        Lower lefthand coordinates of the bounding box contaning the area
        of false flashes
    UR_coords : tuple of str
        Upper righthand coordinates of the bounding box contaning the area
        of false flashes

    Returns
    -------
    filtered_flashes : tuple of lists
        Filtered GLM flash coordinates. Format: (flash_lons, flash_lats)
    """
    filtered_lons = []
    filtered_lats = []

    lons = glm_data[0]
    lats = glm_data[1]

    min_lat = LL_coords[1]
    max_lat = UR_coords[1]

    min_lon = LL_coords[0]
    max_lon = UR_coords[0]

    for idx, lon in enumerate(lons):
        lat = lats[idx]

        if ((lat < min_lat or lat > max_lat) or (lon < min_lon or lon > max_lon)):
            filtered_lons.append(lon)
            filtered_lats.append(lat)

    return (filtered_lons, filtered_lats)