GDS Status & Action Codes Glossary
7 min read · Published · Updated
Every air segment in a PNR carries a two-letter code followed by a number of seats, such as HK1 or HL2. The codes come from the industry's reservations messaging standard (IATA's AIRIMP), which is why Amadeus, Galileo and Sabre agents see the same letters. Some codes are action codes, sent to ask an airline for something (NN: need a seat). Others are advice or status codes, describing what the airline did or what the segment's state is now (HK: holds confirmed; UC: unable). In a retrieved booking you mostly see status codes, but the two-letter field is the same, so they are usually listed together.
Reading the segment EK 902 Y 20AUG AMMDXB HK1 0240 0930, the HK1 means: holds confirmed, one seat. If the same segment later shows TK1, the airline has changed the schedule. If it shows UN1, the flight as booked no longer operates. The status is the fastest way to tell whether a passenger really has a seat on that flight.
Glossary of common codes
This table covers the codes agents meet most often. The same data powers the plain-English status labels in the FlyTix formatter.
| Code | Name | Type | Meaning | What to do |
|---|---|---|---|---|
| HK | Holds confirmed | Confirmed | The airline holds the seat confirmed. | None for the reservation itself. Confirmation is not ticket issuance — check the ticketing elements. |
| KK | Confirming | Confirmed | Airline reply confirming a request (for example a need, NN, or a request, HN). | Acknowledge it so the segment changes to HK, and advise the passenger. |
| RR | Reconfirmed | Confirmed | The segment is confirmed and has been reconfirmed. | None. |
| SS | Sold | Confirmed | Action code used when a segment is sold from availability; normally becomes HK once the booking is finished. | Complete (end) the transaction; check the segment shows HK afterwards. |
| NN | Need | Requested | Action code requesting a seat from the airline. | Wait for the airline's reply (for example KK or UC). |
| HN | Have requested | Requested | A seat has been requested and the airline has not replied yet. | Do not treat as confirmed. Follow up if no reply arrives. |
| HL | Have listed (waitlisted) | Waitlist | The passenger is on the waitlist; no seat is held. | Do not ticket as confirmed. Monitor for KL, or offer an alternative. |
| KL | Confirming from waitlist | Waitlist | Airline reply: a waitlisted segment has cleared and is now confirmed. | Acknowledge it (segment becomes HK) and advise the passenger. |
| TK | Schedule change, confirmed | Schedule change | The airline changed the schedule (times, flight or routing); the passenger is confirmed on the new schedule. | Compare old and new timings, check connections still work, advise the passenger, then acknowledge (to HK). Reissue/revalidate the ticket if required. |
| UN | Unable, flight not operating | Unable / cancelled | The flight does not operate as booked (for example cancelled). | Rebook the passenger and remove the dead segment. If already ticketed, follow the airline's involuntary change policy. |
| UC | Unable, not waitlisted | Unable / cancelled | The airline could not confirm and has not waitlisted the request. | Remove the segment and book an alternative. |
| NO | No action taken | Unable / cancelled | The airline took no action on the request, often because of an error in it. | Check the request, remove the segment and rebook, or contact the airline. |
| HX | Have cancelled | Unable / cancelled | The segment has been cancelled. | Confirm the passenger knows, rebook if needed, and remove the segment. |
| GK | Passive segment | Passive | A passive segment entered for record or ticketing purposes. No booking message is sent to the airline. | Treat as a note, not a reservation: confirm the actual booking exists in the airline's system. |
Other codes exist, and some (including several schedule-change and passive variants) are used differently by different systems and airlines. For any code not listed here, check your GDS provider's help pages before acting on it.
Does the passenger actually have a seat?
The practical question behind every status code is whether the passenger holds a seat. Grouping the codes answers it quickly.
- Seat held: HK, RR, and KK or KL once acknowledged. SS is what you see while selling; after the booking is completed it should show HK.
- No seat yet: NN and HN (requested, waiting for the airline) and HL (waitlisted). Never describe these to a passenger as confirmed.
- Seat held but details changed: TK. The passenger is confirmed, but on a different time, flight or routing from the one originally booked.
- No seat: UN, UC, NO and HX. These segments need to be removed and, usually, rebooked.
- Not a reservation at all: GK is a passive segment. It records a booking made elsewhere and does not send a message to the airline, so it proves nothing about the airline's own inventory.
Codes that need action today
TK: schedule change
TK is the code agents handle most often. The airline has changed something (departure time, flight number, routing) and confirmed the passenger on the new schedule. Before you acknowledge it, compare the old and new timings and check that every connection in the itinerary still works. A small retiming on the first flight can break a minimum connection time on the second. Tell the passenger, then acknowledge the change so the segment returns to HK. If the ticket must be revalidated or reissued to match, do that as well, following the airline's schedule-change policy.
UN, UC and NO: no seat
A UN segment in a ticketed booking is the most urgent case: the passenger holds a ticket for a flight that no longer operates as booked. Rebook, then handle the ticket according to the airline's involuntary change rules. These normally waive the change fee when the airline caused the disruption, but the exact conditions are airline-specific. UC and NO usually appear right after a booking attempt. The seat was not given, so remove the segment and find an alternative rather than leaving a dead line in the PNR.
HL and HN: not yet confirmed
Waitlisted and requested segments look similar to confirmed ones on a busy screen. They are the most common cause of a passenger believing they are booked when they are not. Check the code, not just the presence of the flight, before sending an itinerary. When a waitlist clears, the airline replies with KL. Acknowledge it so it becomes HK, and tell the passenger.
Common mistakes
- Treating HK as proof of ticketing. HK is a reservation status. Whether a ticket exists is shown by the ticketing elements (for example FA lines in Amadeus) or the ticket record, not by the segment status.
- Missing a TK on one segment of a multi-segment trip. Check every segment's status, not just the first.
- Forwarding raw output with HL or HN segments to a passenger, who reads every listed flight as booked.
- Leaving UN/UC/HX segments in the booking. Dead segments clutter the PNR and can confuse reissue and queue processing.
- Treating GK as confirmed by the airline. A passive segment is a record-keeping entry only.
The FlyTix formatter labels each segment's status in plain English and flags any segment that is waitlisted, requested, changed, unable or passive, so these problems show up before an itinerary is sent.
Examples on this page use made-up data. Spotted an error or something that differs in your GDS? Send us a correction.