3.
 Internal ground stop. A ground stop holds aircraft on the ground for a specified amount of time, usually one hour. This initiative is taken when an airport is temporarily overloaded due to arrival bunching or a passing weather system, for example. “Internal” means only arrival flights originating within the same center are affected.

4.
 First Tier GDP. The “first tier” represents a wider affected area than the “internal”. In general, each center’s first tier includes all departure points in the abutting centers. The intent is to include longer flights in the GDP when the problem is expected to last longer. All arrival flights originating in first tier are affected.

5.
 First Tier ground stop.

 6.
 National GDP. Includes all 21 centers.

 7.
National ground stop. Most restrictive initiative for an airport.

How does replanning occur? 1530Z: The graphic arrival picture given by the Aircraft Situation Display (ASD) shows the majority of DFW traffic arriving from the east - from Houston and Memphis ARTCCs. On a normal day the Fort Worth ARTCC is able to delay arrivals within its own airspace to meet the DFW arrival rate. However, if weather slows arrivals, and especially if one out of four corner arrival gates closes, additional delays will need to be absorbed by surrounding ARTCCs. Recognizing this, the SCC NOM proposes that if needed, a miles-in-trail program will be instituted for hand-offs to Fort Worth ARTCC from the surrounding ARTCCs. This telecon is the opportunity for the affected ATC facilities or airlines to comment on or negotiate the solution. Sometimes there may be other factors which need to be considered, but today there is no dissent.
1630Z: The daily afternoon telecon is held with the SCC, FAA Regional offices, ARTCC Traffic Management Supervisors (TMS), and participating airline traffic managers. This time the west coast participates. The agenda is the same as the morning telecon. The group is briefed on the Texas weather situation.
1830Z: The DFW stakeholders are again called to a telecon following a request by Fort Worth ARTCC. The DFW hourly arrival rate has been lowered to 96 from 102. It is decided that the SWAP discussed earlier is to be implemented immediately. Based on the traffic flow picture, miles-in-trail is instituted until 2000Z for all DFW arrivals handed off to Fort Worth ARTCC as follows: Albuquerque: 20 miles, Kansas City - 10 miles, Houston - 15 miles, Memphis - 10 miles.
1920Z: The TMS at Fort Worth ARTCC advises the SCC that the northwest DFW arrival gate at Bowie is being closed due to weather. He coordinates with sector controllers to identify the last aircraft to go through, and begins a plan to re-route arrivals to the remaining corners. The SCC NOM and specialists monitor the situation. Since all of the DFW arrival push traffic is already airborne and close to DFW no additional inter-center flow initiatives are taken except to extend the current SWAP to 2100Z. The problem is now primarily confined to Fort Worth ARTCC and the DFW TRACON and Tower (DFW operates 3 towers during daylight hours).
　
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