Glossary
Plain-English definitions of the operational and commercial measures airlines run on, with how each is calculated and used.
AOGAircraft on ground →
AOG (aircraft on ground) means an aircraft is grounded by a technical problem and cannot fly until it is fixed. It is one of the most urgent situations in airline operations, because a grounded aircraft disrupts every flight it was scheduled to operate.
ASK and RPKAvailable seat kilometres and revenue passenger kilometres →
ASK (available seat kilometres) measures an airline's passenger capacity: seats available multiplied by kilometres flown. RPK (revenue passenger kilometres) measures traffic: paying passengers multiplied by kilometres flown. Dividing RPK by ASK gives the load factor. ASM and RPM are the same measures in miles.
CASKCost per available seat kilometre →
CASK (cost per available seat kilometre) is an airline's operating cost divided by its available seat kilometres (ASK). It is the standard measure of airline unit cost; comparing it with RASK, the revenue per available seat kilometre, shows whether the airline covers its costs.
IATA delay codes →
IATA delay codes are a standard set of codes airlines use to record why a flight departed late. Defined in IATA's Airport Handling Manual (AHM 730), each cause has a two-digit numeric code (and a two-letter alpha equivalent), grouped by area: passengers and baggage, cargo, handling, technical, damage, operations and crew, weather, air traffic control and airports, and reactionary delays caused by earlier flights.
IROPSIrregular operations →
IROPS (irregular operations) is the airline term for disruptions that force the operation off its plan: significant delays, diversions and cancellations caused by weather, technical problems, air traffic control restrictions, crew shortages or airport issues. Managing IROPS means recovering the schedule, the aircraft and crew rotations, and the passengers' journeys.
Load factor →
Load factor is the share of an airline's seat capacity that is filled by paying passengers. It is calculated as RPK (revenue passenger kilometres) divided by ASK (available seat kilometres); for a single flight it is simply paying passengers divided by seats.
OTPOn-time performance →
On-time performance (OTP) is the share of an airline's flights that depart or arrive on time. By common industry convention a flight counts as on time if it departs or arrives within 15 minutes of its scheduled time; it is usually reported as a percentage, separately for departures and arrivals.
RASKRevenue per available seat kilometre →
RASK (revenue per available seat kilometre) is an airline's operating revenue divided by its available seat kilometres (ASK). It measures how much revenue each unit of seat capacity generates and is compared with CASK, the cost per available seat kilometre: when RASK exceeds CASK, the airline makes an operating profit.