I think it has been known for Flow Control to impose a "zero flow rate" occasionally to certain routes for a/c inbound to certain large UK airfields simply to protect the controllers. If you are sat on the ground waiting to get airborne you wouldn't know about any congestion at your destination and this would not be specified in the flow restriction, but I would imagine (or have actually seen) at say Heathrow, the stacks would fill very quickly with anything already airborne from departure points further away. Simple solution, stop anything else getting airborne temporarily until the situation can be controlled safely. Imagine 42 aircraft entering the stacks every hour, the RTF is quite loaded. Then they all ask to divert.............
5mb