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Airline 101

ASK Available seat kilometers, which is the total number of seats available on scheduled flights multiplied by the number of kilometers these seats were flown. ASK will generally be used as the denominator when calculating 'unit cost'
RPK Revenue passenger kilometers, which is the number of paying passengers carried on scheduled flights multiplied by the number of kilometers those seats were flown
Load factor RPK divided by ASK
Breakeven load
factor

Revenue per RPK divided by Cost per ASK

Block hours The time between the departure of an aircraft and its arrival at its destination, as recorded in the aircraft flight log
Aircraft utilisation The amount of time that an aircraft spends in the air carrying passengers
Cost per ASK Total operating expenses (excluding finance costs and taxation) divided by ASK. In the airline industry, this is comparable to 'unit cost'
Revenue per ASK Total revenue divided by ASK
Revenue per RPK Total revenue divided by RPK
Sector length The length of the journey flown by the aircraft
Sector flown Number of times a sector is flown
Bilateral Air Services agreement between two governments
Seat Pitch The distance between one seat and the same point on another seat directly in front or behind
First freedom The freedom to fly across another state without landing
Third freedom The freedom to put down in another state revenue passengers, mail and freight taken on in the state of airline registration
Fourth freedom The freedom to take on in another state revenue passengers, mail and freight destined for the state of airline registration
Fifth freedom rights The freedom that enables airlines to carry passengers to one country, and then fly on to another country (rather than back to their country of origin)
Sixth freedom The privilege for an airline registered in one state to take on revenue passengers, mail and freight in a second state, transport them via the state of registration, and put them down in a third state
Seventh freedom The privilege for an airline registered in one state to take on revenue passengers and freight to a second state and to put them down in a third state without the journey originating, stopping or terminating in the state of registration
'A' checks The basic inspection and routine servicing conducted on an aircraft every 250 hours flown to ensure that the aircraft is in an air-worthy state to continue flying
'C' checks The maintenance performed on an aircraft approximately every 11 months
'D' checks The complete overhaul performed on an aircraft approximately every seven years
Light maintenance Daily routine checks on the aircraft, including daily pre-flight checks and overnight checks, as well as 'A' checks
Heavy maintenance The 'C' and 'D' checks performed on an aircraft
Aircraft push back The act of pushing an aircraft back from a gate or away from other aircraft at parking areas, to allow for an aircraft to begin taxiing under its own power