Block Hours, Flight Hours and Cycles: How ACMI Time Is Counted
Updated: 3 days ago
Three units of time run through every aircraft lease: block hours, flight hours and cycles. They sound technical, but they decide what you pay, and they explain why a lessor quotes one airline a different rate from another for the same aircraft.
Block hours
A block hour runs from the moment the aircraft moves off its parking stand ("chocks off" or "off block") to the moment it stops at the stand at the destination ("chocks on"). It includes taxiing and any waiting on the ground with engines running.
ACMI leases are almost always billed in block hours. So are most minimum guarantees ("minimum 200 block hours per month").
Flight hours
A flight hour runs from take off to landing (sometimes defined as wheels off to wheels on). It excludes taxi time.
Maintenance programmes and engine programmes usually count flight hours, because they measure wear in the air.
On a typical flight, block time is 10 to 30 minutes longer than flight time. At a busy airport with long taxi routes, the difference can be bigger.
Cycles
A cycle is one take off and one landing. Each flight is one cycle, however long it lasts.
Cycles matter because much of an aircraft's wear comes from take off, landing and pressurisation, not from cruising. Landing gear, many engine parts and the fuselage structure have limits counted in cycles, not hours.
Why the ratio matters
The hour to cycle ratio tells a lessor how an aircraft will be used:
Long flights (for example 4 flight hours per cycle): less wear per hour, because each take off is spread over many hours
Short flights (for example 0.8 flight hours per cycle): more wear per hour, because the aircraft takes off and lands far more often
Two lessees flying the same 200 block hours a month can wear the aircraft very differently. The short sector network uses up cycle limited parts much faster.
That is why lessors ask for your planned average sector length, and why:
ACMI rates are often higher for short sector networks
Dry lease maintenance reserves are often set per cycle as well as per hour
Some contracts adjust the rate if the actual ratio differs from the one assumed
A worked example
Two operators each lease a similar regional aircraft for 200 block hours a month.
Operator A flies 45 minute sectors with 15 minutes of taxi on each flight:
Each flight: 1 block hour, 0.75 flight hours, 1 cycle
Per month: 200 block hours, 150 flight hours, 200 cycles
Operator B flies 2 hour 45 minute sectors with 15 minutes of taxi:
Each flight: 3 block hours, 2.75 flight hours, 1 cycle
Per month: 200 block hours, about 183 flight hours, about 67 cycles
Both pay for 200 block hours. But Operator A puts three times as many cycles on the aircraft. A lessor will price that in.
What this means for your quote
When you ask for an ACMI or dry lease quote, give:
Planned block hours per month
Average sector length or a sample schedule
Expected cycles per month
With those, the lessor can price accurately, and you avoid a rate adjustment later. Our ACMI quote checklist lists the other details lessors need.
Getting a quote
Jetvice arranges ACMI and dry leases for passenger and cargo aircraft. Email your network and schedule to info@jetvice.net or see our aircraft leasing page.
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