--- title: "Airline upgrade & loyalty glossary: SWU, GUC, C class" description: "Plain-language definitions of the terms frequent flyers use: SWU, C-class upgrade inventory, GUC, RUC, award vs upgrade availability, IRROPS, CPP, and PNR." canonical: "https://2lnr.com/glossary" url: "https://2lnr.com/glossary.md" --- # Airline upgrade and loyalty glossary 29 travel terms in plain language. Each entry defines one term in a sentence, including the ones that decide whether an upgrade clears: [C-class upgrade inventory](https://2lnr.com/guides/fare-class-availability.md), the certificates that draw on it, and how [award availability differs from upgrade availability](https://2lnr.com/guides/award-availability.md). Terms with a page of their own link straight to it. Search Popular: [IRROPS](#glossary-irrops) [SWU](#glossary-swu) [GUC](#glossary-guc) [RUC](#glossary-ruc) [CPP](#glossary-cpp) [PNR](#glossary-pnr) Showing 29 of 29 terms **Atmos Rewards**\ [Atmos Rewards](https://2lnr.com/about/as/upgrade-certificates.md) Alaska Airlines' loyalty program, which replaced Mileage Plan in 2025 and absorbed HawaiianMiles. Its upgrade certificates are the milestone benefit that clears into first class out of U-class inventory on Alaska and Hawaiian-operated flights. **Award vs Upgrade**\ [Award availability vs upgrade availability](https://2lnr.com/guides/award-availability.md) Two separate inventory pools. Award availability is a premium seat bookable outright with miles; upgrade availability clears a certificate applied to a paid ticket. A flight can have one, both, or neither. **PNR**\ Booking reference Passenger Name Record code used to look up a reservation. **C Inventory**\ [C-class upgrade inventory](https://2lnr.com/guides/aa-c-class-availability.md) American Airlines' upgrade fare bucket. An AA systemwide or miles upgrade confirms only when C class shows open seats on the flight; A class covers Business to Flagship First. **CPP**\ Cents per point Valuation metric: (cash price x 100) / points required. **Codeshare**\ Codeshare flight Flight operated by one airline but sold under another's flight number. **Confirmed upgrade**\ [Confirmed upgrade](https://2lnr.com/guides/how-to-get-upgraded.md) An upgrade on a paid ticket that clears before departure rather than at the gate, which happens only when the airline's upgrade bucket for your instrument shows open seats on that flight: C or A on American, Z, J, P or G on Delta, U on Alaska. When the bucket is at zero the request waitlists, whatever your status. **EQD**\ Elite qualifying dollars Qualifying spend used to earn airline elite status. **EQM**\ Elite qualifying miles Mileage used to qualify for airline elite status. **EQS**\ Elite qualifying segments Flight segments counted toward airline elite status. **GDS**\ Global Distribution System Centralized reservation systems (Sabre, Amadeus) connecting airlines, hotels, and travel agents. **GPU**\ Global Premier Upgrade United upgrade certificate for international or long-haul routes. **GUC**\ [Global Upgrade Certificate](https://2lnr.com/about/dl/global-upgrade-certificates.md) Delta's long-haul upgrade certificate, a Diamond Medallion Choice Benefit that moves you one cabin class higher on Delta-operated flights worldwide and on select partner airlines. It confirms only when the Z, J or P certificate bucket is open on that flight and date, and expires at the end of the Medallion Year it was selected for. **IRROPS**\ Irregular operations Airline disruptions such as delays, cancellations, or gate changes. **MCT**\ Minimum connection time Shortest allowed layover between flights at an airport. **NDC**\ New Distribution Capability Modern airline distribution standard enabling richer content and direct airline connections. **Open Jaw**\ Open jaw itinerary Itinerary where arrival airport differs from departure airport (e.g., fly into Paris, out of Rome). **PUC**\ PlusPoints upgrade United PlusPoints upgrades used to request cabin upgrades. **Portfolio Optimization**\ Portfolio optimization Optimizing across all planned trips simultaneously rather than each trip independently. **Positioning Flight**\ Positioning flight An additional flight taken to reach a departure point with better fares or availability. **RPU**\ Regional Premier Upgrade United upgrade certificate for domestic or regional routes. **RUC**\ [Regional Upgrade Certificate](https://2lnr.com/about/dl/regional-upgrade-certificates.md) Delta's domestic and short-haul upgrade certificate for Platinum and Diamond Medallion members, moving you one cabin class higher on Delta-operated flights. It confirms only when the Z or G certificate bucket is open on that flight, and expires at the end of the Medallion Year it was selected for. **Saver award**\ [Saver award](https://2lnr.com/awards.md) An award seat released in an airline's restricted award bucket for a cabin on a flight: the seats partners can book and the ones that sell out first. Airlines name and price the bucket differently; 2LNR shows whether a seat exists in the bucket it tracks for that carrier, by date, and never what it costs. **SWU**\ [Systemwide upgrade](https://2lnr.com/about/aa/systemwide-upgrades.md) American's one-cabin upgrade certificate, earned as a Loyalty Point Rewards selection from the 175,000 Loyalty Point milestone (up to four at 250,000), valid on American and British Airways flights. It confirms only when C-class upgrade inventory is open on the flight, or A class for Flagship First. **Ticket Chaining**\ Ticket chaining Linking multiple tickets to create complex itineraries, often exploiting pricing advantages. **Travel Triangle**\ Travel Triangle Optimization framework balancing Scope (destinations), Time (flexibility), and Resources (budget). **U (booking class)**\ [U-class inventory](https://2lnr.com/about/as/upgrades.md) On Alaska, the first-class upgrade inventory bucket that both complimentary elite upgrades and upgrade certificates draw from, so a certificate confirms only where U is open. On American, U is the saver award bucket for Business and domestic First; American's confirmed-upgrade bucket is C, not U. **Upgrade Certificate**\ Upgrade certificate An earned instrument that moves a paid ticket to a higher cabin when upgrade inventory opens: AA systemwide upgrades, Delta GUCs and RUCs, Alaska upgrade certificates, United GPUs and RPUs. **Z (booking class)**\ [Z-class inventory](https://2lnr.com/about/dl/upgrades.md) On Delta, the upgrade-certificate inventory code, which is why Global and Regional Upgrade Certificate space can both show as Z; its cabin meaning depends on the airframe, Delta One on widebodies and domestic First on narrowbodies. On American, Z is something else entirely: the First-class saver award bucket, not upgrade space.