SIPP

SIPP stands for Standard Interline Passenger Procedure, a classification system that uses four alphanumeric characters to identify vehicle categories in the car rental industry. It was developed by the International Air Transport Association (IATA) to provide a consistent, neutral way for rental companies to describe vehicle types when selling through travel agents, GDS systems, and other distribution channels. A SIPP code tells you the exact size, drive type, fuel type, and transmission of the car you are getting, regardless of which rental company you book through.

Each SIPP code has four positions. The first letter indicates body type and size: M is a mini, E is economy, C is compact, I is intermediate, S is standard, F is full-size, P is premium, L is luxury, and so on. The second letter describes the transmission and drive: M means manual and front-wheel drive, A means automatic and front-wheel drive. The third position specifies fuel and air conditioning: B is petrol with air conditioning, D is diesel with air conditioning. The fourth position indicates the number of doors and roof type: 2 is two doors, 4 is four doors, C is a convertible. A code like ECAR therefore means economy automatic with petrol air conditioning and four doors.

The system exists because rental companies use different brand names for vehicles of similar size and capability. Without SIPP, a compact car might be called a Focus at one company and a Corolla at another, making it difficult for travel agents to compare prices or guarantee consistency. SIPP abstracts away brand and lets you specify what you actually need. When you book a car through an airline or travel agent, the reservation system converts your SIPP code into the actual vehicle model the rental company will provide.

SIPP codes appear on rental reservations, invoices, and GDS screens (Amadeus, Sabre, Galileo). Travel agents and consolidators rely on them to package car rentals with flights. Rental companies use SIPP internally for fleet management and to standardize quotes across their own websites and affiliates. The codes are case-insensitive and are often shown in uppercase in documentation, though systems may accept lowercase input.

The system has limitations. SIPP does not encode performance, luxury features, or brand prestige, so a premium SIPP code (like PCAR) could represent a high-end sedan or a luxury SUV depending on the rental company's fleet. Regional variants also exist: codes are standardized globally but rental companies in different markets may interpret them slightly differently or offer different models under the same code. When a customer books online directly with a rental company rather than through an intermediary, SIPP may not be visible to them, but it still governs the allocation of vehicles within the rental system.