A resource allocation defines a period of time (which may be open-ended) during which a fixed resource has a defined user. In the case of a flight resource allocation this means assigning the usage of a resource to a particular flight or flights. A non-flight resource allocation may be allocated to a particular task (such as cleaning or maintenance), an airline / airline alliance, a passenger class etc.
Allocations may be exclusive (e.g. to one flight, or airline) or they may not be.