Is there any rule of thumb for how many aircraft of a type an airline should procure in order to have a spare? New anrd/or used aircraft. Of course newer aircraft would break down less than older/used aircraft. Curious if there is a hard and fast rule, or equation, to achieve economies of scale?

Thinking an A220-100 in particular, and lets say 20ys from now on to gauge vintage and corresponding maintenance and availability (not sure what the correct term for this is, dispatch rate?))

I posted in Travel,Polls, Preference but I think more pertinent to here (mods you can delete that one)


Is there any rule of thumb for how many aircraft of a type an airline should procure in order to have a spare for a reliable network? Of course newer aircraft would break down less than older/used aircraft. Curious if there is a hard and fast rule, or equation, to achieve economies of scale?

I'm thinking A220-100s in particular and let's say 20yrs vintage (20yrs from now)

If a new A220-100 is about $80m, i'd guess it would be in $20m range when it's done it's first 20years give or take. Being used it would have more maintenenace of course, but is there any sort of rule of thumb? My guess is maybe 5planes of a type to be able to create a reliable network with a spare included?

May not be a rule of thumb but any guidance is apprecaited.

"Airways News believe that a substantial 65 to 70% discount off the $71.8 million list price was provided making the final sale at $24.6–28.7 million price per aircraft; this large order from a major carrier could help Bombardier to break the Boeing/Airbus duopoly on narrowbody aircraft.[3]" (https://web.archive.org/web/20160429120 ... -customer/ )
A 10-year-old 777 costs only 10 million anyways ( https://pointmetotheplane.boardingarea. ... used-777s/ )

rt23456p wrote:

"Airways News believe that a substantial 65 to 70% discount off the $71.8 million list price was provided making the final sale at $24.6–28.7 million price per aircraft; this large order from a major carrier could help Bombardier to break the Boeing/Airbus duopoly on narrowbody aircraft.[3]" (https://web.archive.org/web/20160429120 ... -customer/ )
A 10-year-old 777 costs only 10 million anyways ( https://pointmetotheplane.boardingarea. ... used-777s/ )

oh wow, maybe a sweetheart deal to get critical mass for the type?

lots of new a220s, 320neos and 321neos sitting around parked due to engine issues.

10% of our brand new NEO fleet is parked and in storage due to no engines.

i thought i read somewhere 5 of 15 Hawaiian's 321s (all relatively new less than 2-3 years old) are parked due to no engines

From experience, North American airlines operate with low single digit operational spare ratios, say 2 - 4% on average.

At U/LCCs that will generally skew lower, at legacies it will skew higher. The smaller the fleet and the larger the operational complexity, the larger the spare ratio necessary to maintain appropriate coverage. Age of aircraft not only plays into reliability but the capital cost of dedicating additional a/c as spares.

Now allocations for other planned maintenance work are also important and definitely do increase with aircraft age (as heavy checks are more likely to uncover issues requiring lengthy work). Paint is another component here, a/c need to be painted every 8-10 years with each paint event generally taking ~2 weeks. Allocations for paint + mx vary seasonally, as airlines will try and consolidate planned work to off-peak periods as much as possible, but can be anywhere from 2 - 20% of a fleet.

Smaller fleets complicate the above - what do you do with your 5-aircraft network if you can't align the planned maintenance work to off-peak periods? What if you have to exit a market for only a month to support necessary mx work? Do you tell business customers, "sorry, not this quarter"? Do you pay 20% of your pilots to do nothing during mx-intense periods?

My personal take is that 8 - 9 aircraft is the minimum necessary: 7 - 8 in schedule, 1 spare, and 0 - 2 in paint / mx. Fleets of ~20 start to achieve economies of scale that probably plateau at a fleet size of around ~100.

RushmoreAir wrote:

From experience, North American airlines operate with low single digit operational spare ratios, say 2 - 4% on average.

At U/LCCs that will generally skew lower, at legacies it will skew higher. The smaller the fleet and the larger the operational complexity, the larger the spare ratio necessary to maintain appropriate coverage. Age of aircraft not only plays into reliability but the capital cost of dedicating additional a/c as spares.

Now allocations for other planned maintenance work are also important and definitely do increase with aircraft age (as heavy checks are more likely to uncover issues requiring lengthy work). Paint is another component here, a/c need to be painted every 8-10 years with each paint event generally taking ~2 weeks. Allocations for paint + mx vary seasonally, as airlines will try and consolidate planned work to off-peak periods as much as possible, but can be anywhere from 2 - 20% of a fleet.

Smaller fleets complicate the above - what do you do with your 5-aircraft network if you can't align the planned maintenance work to off-peak periods? What if you have to exit a market for only a month to support necessary mx work? Do you tell business customers, "sorry, not this quarter"? Do you pay 20% of your pilots to do nothing during mx-intense periods?

My personal take is that 8 - 9 aircraft is the minimum necessary: 7 - 8 in schedule, 1 spare, and 0 - 2 in paint / mx. Fleets of ~20 start to achieve economies of scale that probably plateau at a fleet size of around ~100.

thank you! great info Rush. Spare ratio is the term I was looking for