Activities
Generally, activities of replanning and planning are similar. Usually have to calculate burn and time, figure out where aircraft is now, so use real location, what ATC has told them is their projected route, actual fuel on board, etc., and dispatch does recalculations - minutes and burn, fuel remaining at destination. Dispatch replans the flight plan if the change is required before the flight leaves the gate. When in air, dispatch provides info, doing recalculating of fuel, weight, etc. to see if they can still make destination. Replan is after crew has paperwork, pax loading is set, etc., and something comes up that requires delay, equipage change, route change, etc. Anything where weights change, pax changes, etc. because of some factor. Different numbers than original plan are utilized. Also, if there is a diversion required, dispatch will file a new flight plan from the diversion airport to the original destination if the flight can continue on (e.g., unanticipated stop for refueling). Replanning in the sense of changes to the planned route, speed, altitude, destination STAR or runway, etc. after the aircraft is airborne, is primarily the responsibility of the flight crew, with supporting information from dispatch. They do not re-dispatch. (Which is flight planning from point A to some place along the way -- can’t make it to destination on fuel on board). They will just plan for a fuel stop if they need it.
If changes are things like speeding up to make up time or re-routing around a storm cell, dispatch considers those deviations, not replans. Route deviations are entirely up to the pilot. Flight replanning in the more formal sense of filing a new or modified flight plan while enroute, involves lots of communication between dispatch and the aircraft. For example, dispatch will relay information to the flight crew about new weather or traffic advisories that will likely affect their flight at some point in the future. Sometimes the flight crew will already have this information, and sometimes they will not. If there are changes required in alternates, or a diversion is required, dispatch does the calculations for fuel burn predictions, optimal altitudes, etc. When airplane is in air, joint decision making between crew and dispatch. When diverting for fuel, flight crew will request clearance real time, and make diversion. Then while on ground, new flight plan will be filed. Flight crew will provide position information, fuel remaining, etc. Dispatcher monitors every minute of flight -- gets a lot of alerts that they can convey to flight crew. Dispatch will re-file -- they have autofiling, so plan automatically goes to proper center. For diversions such as mechanical or medical, nearest suitable airport. No questions. Get message from crew, may ask dispatch for weather, ATIS, etc. May be split decision, or crew may make decision on where to go.
Late out of gate. If delay on ground, then causes replanning of fuel, weight, etc. May be on “congo line” -- in line with other aircraft, so you can’t go back to gate or if you do you get on line in last slot. Also winds, fog (on the field). A major issue is whether you are legal to launch (which you aren’t if destination field is below minimums). Once launched, then if airport closes in, different situation. May hold, and then depending on fuel, go to alternate. Dispatch replanning is really focused on before aircraft leaves ground; after in air, general impression is that the crew is the major decision maker, for example as to whether to hold for awhile or to divert. Get info from dispatch, like weather prediction, etc. Once decision is made to divert, dispatch may be involved in planning to alternate, calling alternate airport, etc. Alternates should already have been assessed so diversion is to “acceptable” alternate. But pilots may have to divert to somewhere that isn’t a standard alternate. Have to call FBO (fixed base operator) and see if they can accommodate them. Wherever they divert to, they have to rely on good will to help with situation, pax, fuel, etc. Much more on their own when diverting to an unplanned airport. When diverting to another airport serviced by Spirit, usually because of weather, worry most about which way is weather moving, which affects what further delays are most likely. This is more important than other logistics, pax connections, etc. Talk to crews on the ground at that airport as well.
　
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