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OBS Notes

The OBS field is ALB's short observation and warning slot for one aircraft.

It is there to tell you:

  • something in the route, phase, sequence, or hold picture needs attention
  • ALB is unsure about part of the aircraft's current planning state
  • a tactical event such as a missed approach or broken-off approach has happened

How OBS is shown

  • Some layouts show only the 3-character abbreviation such as RDA or SDR.
  • Internally, ALB has a fixed set of OBS conditions with a display priority.
  • If more than one OBS condition is active at the same time, ALB can cycle between them.
  • Not every active internal condition is always shown. Some notes are suppressed when they are no longer operationally actionable.

OBS notes currently used by ALB

Code Text What it means What usually lies behind it What to check or do
MAP Missed The aircraft is currently treated as a missed approach. ALB's phase logic detected a missed approach from final, landing, or broken-off approach handling. Treat the aircraft as a go-around case first. Rebuild the plan around the missed approach, then let ALB re-sequence it as the situation stabilizes.
BKN BrokenOff The aircraft left the expected final approach picture before landing. ALB detected a broken-off approach. This can include a genuine break-off or a sidestep/re-intercept situation. Check whether the aircraft is re-intercepting the same runway, sidestepping to another runway, or no longer matching the expected final approach.
ODR Overdue Rel The aircraft is overdue relative to its planned release or hold-related timing. ALB sees the planned release timing as late versus the current situation, typically in hold-planning or late-live-basis cases. The note is intentionally suppressed once the aircraft is no longer release-manageable. Check whether the aircraft is still in hold, has left hold later than planned, or now needs the plan rebuilt. Re-plan, re-sequence, or coordinate the hold/timing picture instead of ignoring it.
EST UNST Estimate unstable ALB has route-resolved factual traffic that still has not reached normal first-entry sequencing eligibility. The aircraft appears to belong to the arrival picture, but ALB is deliberately keeping it outside full canonical sequencing until the normal first-entry gate is met. This avoids early prediction and false sequencing confidence. Usually monitor and wait. If it persists unexpectedly, check route, destination, runway, timeline choice, or whether the aircraft really belongs in the active arrival picture. Missing calculations can still show as --- while this informational state is active.
NFX No Fix ALB could not match the aircraft to the expected final fix for the active timeline. The route does not contain the final fix ALB expected for that timeline, or the aircraft no longer matches that final-fix geometry. Check route, runway, timeline choice, and whether the aircraft really belongs in that timeline. If the route updates, the note can clear automatically.
NVF No Via ALB could not resolve the expected via-fix or inbound stream for the aircraft. The aircraft does not fit the expected via-fix stream picture for the active timeline. Check STAR, via-fix assignment, timeline choice, and whether the aircraft belongs in the active stream picture.
RDA Rt Anom Route Distance Anomaly. The route or distance picture looks inconsistent. ALB detected that the route-based geometry or remaining-distance picture does not match what it expects. This is often associated with directs, vectoring, route changes, or a contradictory route-distance value. ALB avoids using grossly contradictory route evidence to drive normal timing or sequencing until the picture is credible again. Check whether the aircraft has been tactically re-routed, vectored, or given directs. If the tactical picture is correct, allow route and geometry data to settle, then use Advance 1 or Resequence only if the aircraft still no longer fits the plan.
SDR Slot Drift The aircraft's live timing is materially late against its committed slot anchor. In LT-style planning, ALB detected the live estimate drifting late versus the slot anchor by at least about a minute. Tactical heading or hold intervention can also be part of the reason. Check whether the aircraft is no longer conforming to the expected plan. If needed, correct tactically, use Advance 1, or Resequence once the aircraft should be returned to normal planning logic.
FPU Phase UKN Flight phase unknown. ALB's phase classifier could not place the aircraft confidently into its normal flight-phase model. Check whether the aircraft has incomplete or unusual live data, route geometry, or a transition state that ALB has not stabilized yet. Often this is a temporary classifier problem rather than an immediate tactical issue.
ASU Arr UKN Arrival state unknown. ALB could not classify the current arrival-state bucket cleanly. Check the aircraft's current relevance to the active timeline and whether the live timing/route state is still settling.
HIG Hold Ign Hold ignored. ALB has deliberately stopped using the current hold data for sequencing because the hold picture appears stale or no longer operationally credible. This can happen in terminal/final phases or when stale hold data persists far from the hold without supporting evidence. Check whether the aircraft is genuinely still in hold, whether HOLDFIX/HOLDEAT information is stale, and whether tracking/controller ownership has changed. Restore the real hold picture or let the stale hold data clear.

Practical reading guidance

  • MAP and BKN are high-priority tactical situation notes.
  • ODR, RDA, and SDR usually mean the aircraft no longer fits the current timing or sequence plan cleanly.
  • EST UNST is different: it is usually a neutral pre-entry information state rather than a tactical warning.
  • NFX and NVF usually mean ALB cannot place the aircraft properly in the current route or stream picture.
  • FPU and ASU usually mean ALB is missing confidence in its internal classification and may need time or cleaner live data.
  • HIG means ALB is protecting the sequencing logic from stale hold data rather than trusting that hold picture blindly.

Resolution pattern

When you see an OBS note, the safest order is usually:

  1. Confirm the aircraft still belongs in the active timeline and view.
  2. Check whether the route, runway, STAR, via-fix, or hold picture has changed.
  3. Decide whether the issue is only a temporary data/classification problem or an actual operational mismatch.
  4. If the aircraft no longer matches the current plan, correct tactically and then use Advance 1 or Resequence when appropriate.

For EST UNST, the usual answer is simpler:

  1. Confirm that the aircraft really belongs to the active arrival picture.
  2. If yes, let ALB wait for normal sequencing entry instead of forcing an early interpretation.
  3. If no, fix the route, runway, or timeline context that made the aircraft look relevant in the first place.