diff --git a/fix-1-1-2-emms-extension.py b/fix-1-1-2-emms-extension.py
new file mode 100644
index 0000000..47dbc34
--- /dev/null
+++ b/fix-1-1-2-emms-extension.py
@@ -0,0 +1,167 @@
+"""
+Re-write 1-1-2 aviation emissions files
+"""
+
+from __future__ import annotations
+
+import shutil
+from pathlib import Path
+
+import netCDF4
+import numpy as np
+
+
+def add_correct_time_bounds(
+    ds: netCDF4.Dataset,
+    ds_fixed: netCDF4.Dataset,
+    bounds_time: str = "time_bnds",
+) -> netCDF4.Dataset:
+    """
+    Add the correct time bounds
+
+    Parameters
+    ----------
+    ds
+        Dataset from which to get the original data
+
+    ds_fixed
+        Fixed dataset from which to get the correct time bounds
+
+    bounds_time
+        Name of the variable to use for time bounds
+
+    Returns
+    -------
+    :
+        `ds_fixed` with time bounds applied
+
+        Note that the operation is in place,
+        so returning this is just a convenience.
+    """
+    if "bound" not in ds.dimensions:
+        raise AssertionError
+
+    # ds_fixed.createVariable(bounds_time, ds["time"].datatype, ("time", "bound"))
+
+    time_int = ds["time"][:]
+    time_date = netCDF4.num2date(
+        time_int,
+        units=ds["time"].getncattr("units"),
+        calendar=ds["time"].getncattr("calendar"),
+    )
+    bounds_time_fixed_l = []
+    # Loop, crazy slow, whatever
+    n_months_in_year = 12
+    for v_int, v_date in zip(time_int, time_date):
+        start_of_bound_date = type(v_date)(v_date.year, v_date.month, 1)
+        if v_date.month == n_months_in_year:
+            end_of_bound_date = type(v_date)(v_date.year + 1, 1, 1)
+
+        else:
+            end_of_bound_date = type(v_date)(v_date.year, v_date.month + 1, 1)
+
+        bounds_time_fixed_l.append(
+            [
+                netCDF4.date2num(
+                    v,
+                    units=ds["time"].getncattr("units"),
+                    calendar=ds["time"].getncattr("calendar"),
+                )
+                for v in [start_of_bound_date, end_of_bound_date]
+            ]
+        )
+
+    bounds_time_fixed = np.array(bounds_time_fixed_l)
+    ds_fixed.variables[bounds_time][:] = bounds_time_fixed
+
+    return ds_fixed
+
+
+def rewrite_file(
+    fp: Path,
+    out_dir: Path,
+    verbose: bool = True,
+):
+    """
+    Re-write anthropogenic emissions file
+
+    Parameters
+    ----------
+    fp
+        File path to rewrite
+
+    out_dir
+        Directory in which to write the rewritten file
+
+    verbose
+        Should lots of information be printed?
+    """
+    fixed_file = out_dir / fp.name
+    if verbose:
+        print(f"Rewriting {fp} to {fixed_file}")
+
+    shutil.copy2(fp, fixed_file)
+    ds = netCDF4.Dataset(fixed_file, "a")
+    ds_original = netCDF4.Dataset(fixed_file, "r")
+
+    ds = add_correct_time_bounds(ds_original, ds)
+
+    ds["time"].setncattr("bounds", "time_bnds")
+    ds["time_bnds"].delncattr("units")
+    ds["time_bnds"].delncattr("calendar")
+
+    ds.close()
+    ds_original.close()
+
+
+def main():
+    """
+    Re-write the files
+    """
+    for dd in [
+        "vl-ext_1-1-2",
+        "l-ext_1-1-2",
+        "ln-ext_1-1-2",
+        "ml-ext_1-1-2",
+        "m-ext_1-1-2",
+        "hl-ext_1-1-2",
+        "h-ext_1-1-2",
+    ]:
+        source_dir = (
+            Path(
+                "/global/cfs/projectdirs/m4931/zrjn-tmp/20260804-aviation-scenarios-extensions"
+            )
+            / dd
+        )
+        tmp_dir = Path(
+            "/global/cfs/projectdirs/m4931/zrjn-tmp/20260804-aviation-scenarios-extensions-rw"
+        )
+        # OUT_DIR = Path("../input4MIPs_CVs/vl-cf-emms-rw")
+
+        # CV_SOURCE = "../input4MIPs_CVs"
+
+        tmp_dir.mkdir(exist_ok=True, parents=True)
+
+        for f in source_dir.glob("*.nc"):
+            rewrite_file(f, tmp_dir)
+
+    # OUT_DIR.mkdir(exist_ok=True, parents=True)
+    # for tmp_file in TMP_DIR.glob("*.nc"):
+    #     out_file = rewrite_file_in_drs(
+    #         tmp_file, output_root=OUT_DIR, cv_source=CV_SOURCE
+    #     )
+    #
+    #     validation_res = get_validate_file_result(
+    #         out_file,
+    #         cv_source=CV_SOURCE,
+    #         # xr_variable_processor=xr_variable_processor,
+    #         # frequency_metadata_keys=frequency_metadata_keys,
+    #         # bounds_info=bounds_info,
+    #         # Allow issues with units for sector
+    #         allow_cf_checker_warnings=True,
+    #     )
+    #     validation_res.raise_if_errors()
+
+
+if __name__ == "__main__":
+    main()