When you file a flight plan, either VFR or IFR, the procedure begins the same way: by calling the Flight Service Station or via DUAT online. Even the same form is used for either flight plan. But when you hang up the telephone a VFR and an IFR flight plan go their separate ways.
THE VFR FLIGHT PLAN
When the FSS briefer receives your VFR flight plan and hangs up the phone, they really don’t do anything with it. It is placed in a box and it will sit in that box until you activate that flight plan. A certain number of flight plans that are called in are never activated. Maybe the pilot changes their mind, or the weather gets worse, or the pilot simply forgets or does not know how to activate the flight plan once in flight.
How it Works: The FSS will hold the flight plan for one hour past the proposed departure time — then they are thrown away. When a VFR pilot does call in and activates the flight plan, the FSS briefer still does not do much with it. Sometimes the destination of the flight lies within the jurisdiction of that very same FSS. In that case, the flight plan is moved to an active box and sits there during the flight. If the destination airport lies within the jurisdiction of another FSS, then only the pertinent information is sent to the receiving FSS: airplane number, destination, and proposed time of arrival. It is possible for a VFR flight plan to be completely handled by a single individual. One briefer could take the plan over the phone, activate the plan when the pilot radios in, and cancel the plan when the pilot calls back after landing. Even when more than one FSS briefer is involved, the VFR flight plan never leaves the ‘possession’ of the FSS — in other words, air traffic controllers never get involved with VFR flight plans.
THE IFR FLIGHT PLAN
What happens to an IFR flight plan is very different. When the FSS briefer receives an IFR flight plan and hangs up the phone, rather than sticking it in a box, they immediately relay the information to the nearest Air Route Traffic Control Center (ARTCC). When the IFR flight plan is received at the ARTCC, its information is fed into the system computer, which analyses the plan.
How It Works: The computer looks at the departure point and departure time, the route selected, and the destination airport and arrival time. Your plan is compared with thousands of others for possible conflicts and delays. If you have made an error in writing out your flight plan, such as an incorrect route of flight or altitude, the computer can kick out your plan altogether. The plan can be altered to correct mistakes or to avoid obvious delays. You might be assigned a ‘preferred route‘ rather than the route you selected, because of prevailing traffic flows. The computer can accept your plan ‘as filed,’ which means it was approved just as you originally wrote it. When the ARTCC accepts or amends your flight plan, it becomes a ‘clearance.’ This all takes some time, so pilots are advised to allow at least 30 minutes between filing the plan and asking for the clearance.
The clearance is then passed from the ARTCC, to the nearest air traffic control facility to the departure point. The pilot must now ask for the clearance to start the ball rolling. Before the end of this flight, that original flight plan could be handled by dozens of people. The clearance will be passed inside the ATC system from the ‘clearance delivery’ controller, who just as the name implies delivers the clearance to the pilot, to ground control, to the tower, to departure control.
In Flight: After takeoff, the clearance is passed from a terminal’s departure controller to the ARTCC. The ARTCC is made up of twenty or more ‘sectors’ and your course might take you across several sectors. Each sector has a different controller and each controller handles, then passes along, your clearance. As you approach your destination, the ARTCC sector controller whose airspace is adjacent to the approach control airspace will ‘handoff’ you and your clearance to the approach controller. The approach controller puts you in the line of traffic all headed for an instrument approach and eventually hands you off to the control tower.
Post-Flight: Finally, when you land at an airport with an operating control tower your IFR flight plan is cancelled automatically. If you land with an IFR clearance where there is no operating tower, the IFR flight plan must be canceled, much like a VFR plan, by calling the FSS. A VFR flight plan is not cancelled by the control tower. (Remember, controllers never touch a VFR flight plan … they don’t even know if you are on a VFR flight plan or not.)
APPLES AND ORANGES
You can see that the commitment in manpower involved in an IFR flight plan is quite different than for the VFR flight plan. There can easily be 25 or more people involved with the IFR flight plan of a Cessna 172. The world of IFR has many players all attempting to pass aircraft through the system continuously and smoothly. When you become instrument rated you become one of those players.
There are many ways that an IFR clearance is passed to the pilot. Mishandling this handoff can cause confusion and danger. Next week, we’ll discuss how to make this vital pass of information flawless and safe.