I agree with
@757Geek here, and I was not precise enough with my terminology before. The title of OpSpec B044 is "Planned Redispatch or Rerelease Enroute," with the term "planned" being included for a reason. The definition pulled straight from B044 is, "a planned redispatch or rerelease is one that is planned before takeoff to be redispatched or rereleased, in accordance with §121.631(f) at a predetermined point along the route of flight to an airport other than that specified in the original dispatch or flight release." The referenced 121.631(f) also makes it clear that an unplanned redispatch/rerelease can occur when the destination is changed to any airport other than the originally planned destination: "No person may change an original destination or alternate airport that is specified in the original dispatch or flight release to another airport while the aircraft is en route unless the other airport is authorized for that type of aircraft and the appropriate requirements of §§ 121.593 through 121.661 and 121.173 are met at the time of redispatch or amendment of the flight release."
While redispatch/rerelease (distinct from "planned redispatch/rerelease") is not expressly defined anywhere, it is clear based on the term's usage in B044, 121.631(f), and 121.533(c)(3)/121.535(c)(3) that an unplanned redispatch/rerelease is a change of destination to an airport other than the original destination. Dispatching a flight is releasing it to a specific airport (the original destination) in compliance with all 14 CFR requirements (including weather minimums, alternates, etc.). You can
amend any part of the dispatch release other than the destination, including changing the planned alternate. Once it is decided that the flight will divert to the planned alternate or any other suitable airport, then the flight is
redispatched/rereleased to the new destination since the original destination has been changed. In essence, my interpretation of 121.533, 121.535, and 121.631 is that a flight must be dispatched or released to any airport intended as a destination. If the destination changes any time after the dispatch release has been signed (including when the flight is enroute), the requirement for a legal release to the new destination airport is still in effect (hence the term redispatch or rerelease). The exception to this rule would be when the PIC's emergency authority is exercised.
I do object to rerelease and amend being used interchangeably because the term rerelease is specifically used for B044 operations under supplemental rules. Since supplemental operations do not have dispatchers (rather, "persons who exercise operational control" or flight followers), the flight must be released (rereleased) rather than dispatched (redispatched). The first paragraph of B044 states, "The certificate holder is authorized to conduct planned redispatch for flag operations or
planned rerelease for supplemental operations."
I know this is all semantics in some sense, but terms like the above can be used rather loosely and become confusing when actually examined. What I would define each term as is:
AMEND: To change any aspect of the flight plan, other than the destination. This would include planned alternates, fuel numbers, routes, DMIs, and other non-destination aspects.
Ref: 121.631(b) and 121.631(f).
REDISPATCH: Applicable to domestic and flag operations. The act of changing the destination to another C070 airport, whether or not the new destination was the planned destination alternate.
Ref: 121.533(c)(3) for domestic, 121.535(c)(3) for flag, and 121.631(f) for both.
RERELEASE: Applicable to supplemental operations. The act of changing the destination to another suitable airport within authorized B050 areas of operation, whether or not the new destination was the planned destination alternate.
Ref: 121.631(f). The term release, rather than dispatch, is used per the above definition from the first sentence of B044.
PLANNED REDISPATCH: Applicable to flag operations. A redispatch that has been planned in accordance with B044, with all required information listed on the original flight plan.
Ref: B044.
PLANNED RERELEASE: Applicable to supplemental operations. A rerelease that has been planned in accordance with B044, with all required information listed on the original flight plan. The difference is terminology is due to the legal operational control differences between flag dispatchers and supplemental flight followers.
If anyone has a different interpretation, I am open to it. I just think it's important to be clear on the terminology when it can easily become muddled.