If you already know that HK means confirmed and HL means waitlisted, this guide goes further — covering the full range of action and status codes you'll encounter across a GDS career, organized by what they actually mean for the booking. Status confusion is one of the more common GDS challenges agents run into day to day, and it only gets more confusing once you're switching between systems — see the GDS Commands Hub for the full command reference across Amadeus, Sabre, and Galileo/Apollo.
For a beginner-friendly introduction to the three most common codes first, see our HK vs HL vs KK guide. This page is the complete reference once you're ready to go beyond the basics.
Confirmed Status Codes
| Code | Meaning |
|---|---|
| HK | Holding Confirmed — segment is confirmed |
| KK | Confirmed — airline's response confirming a previously requested segment |
| KL | Confirmed from waitlist — airline has cleared a waitlisted segment |
| RR | Reconfirmed — used in some markets requiring reconfirmation of onward segments |
Waitlisted / Pending Codes
| Code | Meaning |
|---|---|
| HL | Have Listed — passenger is waitlisted for the segment |
| PN | Pending — a request has been made but not yet actioned |
| NN | Need — a new request awaiting airline action |
Unable / Cancelled Codes
| Code | Meaning |
|---|---|
| UN | Unable — the airline could not accommodate the segment, typically because that specific flight isn't operating |
| UC | Unable, waitlist Closed — the airline can neither confirm nor waitlist the request |
| HX | Have Cancelled — the segment is no longer active. Most often follows an airline-side operational change, though it can also result from an agent or GDS-side cancellation action, so the exact trigger isn't always obvious from the code alone |
| XX | Cancelled segment (older/alternate notation for the same inactive status as HX in some system displays) |
Schedule Change / Action Codes
| Code | Meaning |
|---|---|
| TK | Two different meanings depending on where it appears — see below |
| SC | Schedule change notification from the airline, awaiting agent action |
| NO | No action taken yet on a request |
| GK | Airline-initiated confirmation without a prior request (a "gift" segment added by the carrier) |
Why TK Means Two Different Things
TK is the code that trips up more people than any other on this list, because it shows up in two unrelated places with two unrelated meanings. As one of the five mandatory elements every PNR needs before it can be saved, TK marks the ticketing arrangement — the deadline by which the ticket must be issued. That has nothing to do with the flight schedule.
Separately, TK can appear as a segment status code sent by another airline, meaning a schedule change has occurred and the times have shifted, though the booking still holds. In this context it's telling you to check the new departure and arrival times, not a ticketing deadline. The two uses look identical — same two letters — but which one applies depends entirely on whether the TK is sitting in the booking's required-elements section or next to a specific flight segment.
Codes can vary slightly in meaning by GDS and by airline-specific configuration in rare cases. When in doubt on a specific booking, the safest confirmation is always the airline's own system, but the codes above cover the vast majority of what you'll see day to day.
Why Agents Care About Inactive Codes Even After Rebooking
There's a consequence to codes like UN, UC, and HX that goes beyond just knowing what they mean. Airlines expect agencies to clear inactive segments out of a PNR within a set window before departure, often 24 hours. Leaving one sitting past that window can trigger an Agency Debit Memo (ADM) — a fee charged back to the agency for not cleaning up the booking. If you're an agent and see one of these codes lingering, it's not just a display issue to note and move on from; it's worth actively cancelling or rebooking that segment before it becomes a billing problem.
Why Getting This Right Matters
Sending a client an itinerary that still shows HL as if it were confirmed is one of the more common — and most avoidable — mistakes new agents make. Always double-check the status column before sharing an itinerary, and don't assume every two-letter code means "confirmed" just because a segment appears in the PNR.
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