The forwarder issues a house air waybill to each shipper whose cargo it consolidates, the airline or its agent issues one master air waybill for the consolidated shipment, and that single master can cover the house air waybills of several shippers. The house document is the forwarder's contract with the individual shipper and carries the specific details of that shipment; the master is the contract of carriage with the airline and covers the whole journey from origin to destination. The trap is carrying ocean release logic into air: an air waybill at either level is never a document of title, so cargo releases to the consignee named on the document rather than against surrendered originals. For the forwarder, control over delivery sits in who is named as consignee at issuance, which is the detail to get right before the shipment departs.
Glossary
MAWB vs HAWB
The pair of air waybills covering the same cargo: the master air waybill (MAWB), issued by the airline or its agent for the consolidated shipment, and the house air waybill (HAWB), issued by the freight forwarder to the individual shipper within that consolidation.