<xs:attribute name="DateChangeNbr" use="optional">
    <xs:annotation>
        <xs:documentation xml:lang="en">When present contains the number of days by which the flight's arrival date differs from its departure date.</xs:documentation>
    </xs:annotation>
    <xs:simpleType>
        <xs:restriction base="xs:string">
            <xs:enumeration value="-1">
                <xs:annotation>
                    <xs:documentation xml:lang="en">The date of arrival is 1 day before the departure date.</xs:documentation>
                </xs:annotation>
            </xs:enumeration>
            <xs:enumeration value="+1">
                <xs:annotation>
                    <xs:documentation xml:lang="en">The date of arrival is 1 day after the departure date.</xs:documentation>
                </xs:annotation>
            </xs:enumeration>
            <xs:enumeration value="+2">
                <xs:annotation>
                    <xs:documentation xml:lang="en">The date of arrival is 2 days after the departure date.</xs:documentation>
                </xs:annotation>
            </xs:enumeration>
        </xs:restriction>
    </xs:simpleType>
</xs:attribute>