GDS Status & Action Codes Glossary
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Every segment line in a GDS PNR carries a two-letter code that describes the current state of that reservation. These codes are broadly divided into two categories: status codes and action codes. Status codes report what the airline has confirmed — for example HK for a seat the airline holds confirmed. Action codes communicate what the GDS is requesting of the airline, or what the airline is requesting of the agent — for example TK when the airline has made a schedule change and expects the agent to acknowledge it. In practice the same abbreviation can function as both, depending on which direction the message flows, which is why GDS documentation groups them together under the umbrella term status/action codes.
The codes appear immediately after the route field on the segment line. Reading a PNR segment like EK 902 Y 20AUG AMMDXB HK1 0240 0930, the HK1 component is the status code: HK tells you the status (confirmed), and the digit 1 tells you how many seats that status applies to. When the two-letter status changes — for example from HK1 to TK1 after an airline schedule change — that is the signal that action is required.
Complete glossary of status and action codes
| Code | Name | Meaning / action |
|---|---|---|
| HK | Holds confirmed | The airline has confirmed the seat. No action required by the agent. |
| HL | Have listed (waitlisted) | The passenger is waitlisted. Monitor for confirmation or advise the passenger to consider alternatives. |
| HN | Have need (requested) | The seat has been requested from the airline but no confirmation has been received yet. Monitor for a response. |
| HX | Have cancelled | The segment has been cancelled by the agent or the airline. Verify the passenger is aware and rebook if needed. |
| KK | Confirm (airline reply) | The airline has confirmed the booking in response to a KL or KP request. Advise the passenger. |
| KL | Confirm list (waitlist confirmed) | The airline has confirmed a previously waitlisted segment. Advise the passenger that their waitlist cleared. |
| TK | Schedule change — advise passenger | The airline has changed the schedule (time, equipment, or routing). Review the new details and reconfirm or reissue as needed. |
| TL | Schedule change — ticketing limit | The schedule change also affects the ticketing deadline. Reissue or reconfirm before the new limit. |
| UN | Unable (flight unable) | The airline cannot confirm this segment — the flight may be cancelled, the route may no longer operate, or the class is not available. Rebook the passenger. |
| UC | Unable — waitlist closed | The airline is unable to list the passenger even on a waitlist. Find an alternative routing. |
| US | Unable — segment previously sold | The airline has been unable to reconfirm a previously sold segment. The booking is at risk; contact the airline or rebook. |
| NO | No action taken | The airline received the request but took no action. Follow up directly with the airline. |
| SC | Schedule change (informational) | The airline notified the GDS of a schedule change. Confirm the new details match the passenger's plans. |
| PN | Pending (reply requested) | A response from the airline is pending. Do not assume confirmation; wait for a KK or HK reply. |
| RR | Reconfirmed | The segment has been reconfirmed with the airline directly. Often used after a phone reconfirmation on interline segments. |
| DK | Decline confirmed | The airline has declined the booking. Rebook the passenger in an available class. |
| GK | Guaranteed / confirmed by GDS | Confirmation generated by the GDS on behalf of the airline. Treat as confirmed, but verify on long-haul or interline segments. |
| BK | Booked | Segment has been booked. Used by some airlines as an initial confirmation state before full HK status is assigned. |
Confirmed, requested, and unable: grouping the codes
The codes divide naturally into three groups based on what they tell you about the current state of the booking.
Confirmed codes: HK, KK, KL, RR, GK, and BK all indicate that a seat has been allocated and the booking is active. Of these, HK is by far the most common in a retrieved PNR — it is the standard confirmed state that most segments should be in by the time the passenger travels. KK and KL appear after a specific confirmation exchange between the GDS and the airline, and RR typically reflects a manual reconfirmation. GK is a GDS-generated confirmation that may not always have been acknowledged directly by the airline, so it is worth verifying on interline itineraries.
Requested and pending codes: HN, PN, and NO indicate that the booking is in progress but not yet confirmed. HN is the normal state during the brief window between the agent's booking request and the airline's reply. PN signals that the agent or system is actively waiting for a response. NO is more concerning — it means the airline received the request but did not act on it, which may indicate a technical issue or a class-availability conflict that requires the agent to follow up.
Unable codes: UN, UC, and US indicate that the booking cannot proceed as requested. UN is the most common — the airline cannot provide the segment as booked, usually because the flight has been cancelled or the class is no longer available. UC means not only can the airline not confirm the booking, it also will not place the passenger on a waitlist. US indicates a previously confirmed segment has failed reconfirmation. All three require the agent to rebook the passenger on an alternative routing or flight.
Codes that require immediate action
Certain codes represent not just information but explicit requests for agent action, and leaving them unresolved can result in lost bookings or passenger disruption.
TK (schedule change, advise passenger) is one of the most common action codes an agent encounters. The airline has modified the schedule — changed the departure time, substituted a different aircraft, or altered the routing — and has flagged the booking to prompt the agent to review the change and either accept it (which updates the segment to HK) or reject it and rebook. Until the agent acknowledges a TK, the booking remains in an unresolved state. Passengers who are not informed of the schedule change may arrive at the airport with outdated timing information.
TL (schedule change with updated ticketing limit) adds urgency: not only has the schedule changed, but the deadline for ticketing this segment has also moved. Missing the new ticketing deadline typically means the fare is repriced at current market rates, which may be significantly higher.
UN and UC (unable codes) require the agent to rebook the passenger. A segment sitting in UN status in a PNR that has already been ticketed is particularly critical — the passenger holds a ticket for a flight that no longer exists as booked. The agent must rebook and reissue, usually under the airline's involuntary rerouting rules, which generally waive change fees and fare differences when the airline caused the disruption.
KK and KL (airline confirmation replies) are positive codes but they still require action: the agent should notify the passenger that a waitlisted segment cleared or that the booking has been formally confirmed by the airline, and where appropriate update the ticketing.
Status and action codes are broadly shared across Amadeus, Galileo, Sabre, and other GDS platforms, as they derive from common IATA airline reservation messaging standards. However, minor differences in how individual systems present or trigger certain codes do exist — always verify against your host system's documentation for codes you encounter infrequently.