Closing an F-PLN Discontinuity
PremiumbeginnerThe F-PLN DISCONTINUITY line is not an error message. It is the FMGS telling you it does not know how you intend to join two pieces of route.
What this scenario covers
A discontinuity appears wherever the flight plan has a gap the box cannot fill on its own — typically between the end of a departure procedure and the start of the enroute portion, or between an arrival and an approach. Rather than guess a track, the FMGS marks the join and waits.
Closing it is a clear-and-connect operation on the F-PLN page: remove the discontinuity so the waypoint before it links straight to the waypoint after. The result you are looking for is a continuous route with sensible distances either side of the join.
How it applies in flight ops
Discontinuities matter because managed lateral navigation will not fly through one. Left in place, the aircraft flies to the last waypoint before the gap and then keeps its heading — which is fine if you meant to be vectored, and very much not fine if you thought the aircraft was following the plan.
Real crews leave them in deliberately sometimes: a discontinuity after the last SID waypoint is an honest representation of "expect vectors". The skill is knowing which of your discontinuities are intentional.
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The MCDU checks every entry as you make it, and tells you when an entry was accepted but wrong.
Step-by-step: Closing an F-PLN Discontinuity
- Enter a route to work with. Type EGLL/LFPG into the scratchpad and press 1R.
EGLL is London Heathrow, LFPG is Paris Charles de Gaulle. As soon as you enter FROM/TO, the FMS has two endpoints but no path between them — so it inserts a discontinuity to mark the gap it cannot connect on its own.
- Press the F-PLN key to open the flight plan and see the discontinuity.
A discontinuity (shown as ---F-PLN DISCONTINUITY---) is a deliberate break in the route. The FMS will NOT fly across it — in the real aircraft, reaching a discontinuity drops the autopilot out of managed NAV and it flies straight ahead. That is why you must close every discontinuity before departure. It is not an error; it is the FMS telling you "I don't know how to join these two points — you decide."
- Fill the gap. Type MID into the scratchpad, then press 2L — the line select key next to the discontinuity line. MID takes that line, and the discontinuity moves down below it.
MID is the Midhurst VOR, where Heathrow's Paris traffic joins the airways. A waypoint you type onto the flight plan goes in at the line you press, and the FMS puts a discontinuity after it — the Airbus FCOM says a waypoint inserted directly "creates a discontinuity between the new waypoint and the previous one". Typing onto the discontinuity line follows the same rule: the gap is pushed down, not removed. Note the difference from an EMPTY scratchpad: pressing a waypoint's line key with nothing typed opens the LAT REV menu instead.
- Add the next point. Type BOGNA and press 3L — the discontinuity line again, now below MID. BOGNA goes in, and the discontinuity moves down once more.
BOGNA is on the south coast, the next point on the route to Paris. However many waypoints you type in, the discontinuity stays in front of the destination until you remove it yourself: the FMS will not decide on its own that BOGNA joins LFPG.
- Now close the gap. With the scratchpad empty, press CLR — the scratchpad shows CLR — then press 4L, the key beside the discontinuity. Your route is now continuous: EGLL → MID → BOGNA → LFPG.
CLR followed by a line key is the Airbus clear function: on a waypoint it deletes the waypoint and leaves a discontinuity, and on a discontinuity — in the FCOM's words — "the discontinuity can also be cleared in a similar way". Clear one only when you mean the waypoints either side of it to be joined: a discontinuity you clear becomes a leg the FMS will fly. With none left, the FMS can fly the whole path in managed NAV.
What to take away
- A discontinuity is a gap the FMGS refuses to guess across, not a fault.
- Managed NAV will not fly through one — the aircraft continues on heading.
- Close it on F-PLN so the waypoints either side connect directly.
- Some discontinuities are intentional; know which of yours are.
The rest of Flight Plans & Routing
London Heathrow to Paris CDG
beginnerA complete short-haul setup, gate to gate on paper: London Heathrow to Paris Charles de Gaulle, the sector every A320 pilot in Europe has flown a hundred times.
📍 EGLL → MID → BOGNA → HARDY → XIDIL → BIBAX → LFPG (via L612, M605, UM605)⏱ ~7 min📊 23 stepsSID & STAR: KPHX → KLAS
intermediateYour first real procedure practice: pick a departure out of Phoenix and an arrival into Las Vegas, from the trainer's real FAA procedure data.
📍 KPHX → KLAS — SID + STAR practice⏱ ~5 min📊 5 stepsAIRWAYS Entry & the "NOT IN DATABASE" Fix
PremiumintermediateThe "NOT IN DATABASE" message is the single most common thing to go wrong when entering an airway. Here is why it appears and how to insert an airway properly — L612, the first airway from London to Paris.
📍 EGLL → MID → BOGNA → LFPG (via L612)⏱ ~5 min📊 9 stepsRoute Correction
intermediateYou typed the wrong destination. Every pilot has. The skill being practised is not avoiding the mistake — it is catching it and clearing it out cleanly.
📍 EGLL → MID → BOGNA → LFPG (via L612)⏱ ~3 min📊 10 steps
Background reading
- GuideWhy LNAV Doesn't Work When You Turn On the Autopilot
LNAV engaged but the aircraft flies straight past the magenta line in MSFS 2024? The 6 most common causes on the PMDG 737 and Airbus A320 — and the fix.
- GuideThe A320 MCDU Explained: Every Page, Simply
What is the A320 MCDU? A plain-English guide to every Airbus MCDU page — INIT, F-PLN, PERF, RAD NAV and more. Practice free in our MCDU trainer.
- GuideThe Boeing 737 CDU / FMC Explained: Every Page
What is the 737 CDU and FMC? A plain-English guide to every Boeing 737 CDU page plus the EXEC/MOD workflow. Practice free in our CDU trainer.