<xs:attribute name="Method" use="optional">
    <xs:annotation>
        <xs:documentation source="Description" xml:lang="en">The allowance method.</xs:documentation>
    </xs:annotation>
    <xs:simpleType>
        <xs:restriction base="xs:string">
            <xs:enumeration value="D - Direct Settlement" />
            <xs:enumeration value="EA - EMD Associated" />
            <xs:enumeration value="ES - EMD Standalone" />
            <xs:enumeration value="F - Fare Integrated" />
            <xs:enumeration value="MA - Flight Associated Settled via MCO" />
            <xs:enumeration value="MA - Standalone Settled via MCO" />
        </xs:restriction>
    </xs:simpleType>
</xs:attribute>