CarrierGroup 

Either the carrier for the segment or a number of carriers that can be
used for the segment

Element Group Information

Model

Carrier | Carriers
Children: Carrier, Carriers

Used By

Element Carriers
Element Group LocationRangeGroup
Complex Types CarrierType, FlightType, SegmentAirType, SegmentRailType, SegmentRoadType, SegmentTransferType, SegmentTransportationType, SegmentWaterType

Source 

<xs:group name="CarrierGroup">
  <xs:annotation>
    <xs:documentation>Either the carrier for the segment or a number of carriers that can be used for the segment</xs:documentation>
  </xs:annotation>
  <xs:choice>
    <xs:annotation>
      <xs:documentation>One or many</xs:documentation>
    </xs:annotation>
    <xs:element ref="Carrier"/>
    <xs:element ref="Carriers"/>
  </xs:choice>
</xs:group>