Flight length: how long is long enough
Flight length in a fixed-location channel is determined by how long it takes for the audience to cycle through the stores. A shopper who visits weekly needs a flight of several weeks to have a reasonable chance of multiple exposures; one who visits daily accumulates frequency much faster.
That makes flight length a function of visit frequency rather than a media convention.
What does a short flight deliver?
High frequency among frequent visitors and very little reach among occasional ones. In a store channel, the frequent visitors are a substantial share of traffic, so a short flight is not wasted — it is simply concentrated.
Whether that suits the objective is the question. An awareness objective needs breadth; an activation objective aimed at regulars may be well served by concentration.
What does a long flight deliver?
Broader reach as less frequent visitors cycle through, and rising frequency among regulars that eventually exhausts the creative. Both effects run simultaneously, which is why long flights need rotation.
There is also a diminishing return: after the frequent visitors have seen the message several times, additional weight reaches mostly the same people again.
How do you estimate the right length?
From the store's visit frequency distribution. If most traffic comes from shoppers visiting several times a week, a few weeks covers most of the audience; if visits are weekly or less, the flight has to be longer to reach the same proportion.
That distribution is derivable from transaction data in a network with point-of-sale visibility, which is a real planning advantage.
What about always-on?
Always-on presence suits brands whose purchase occasion recurs and whose competitive position depends on continuous visibility. It requires a rotation plan and it accumulates reach across the full visitor distribution rather than only the frequent segment.
The trade is that weight is spread thin. Continuous presence at low share of voice and concentrated presence at high share are different strategies, and the choice should be deliberate.
How does this interact with a promotion?
A promotional flight should cover the promotion, and it usually should not extend far beyond it. Media running after a promotion ends drives shoppers to a price that no longer exists, which is worse than no media.
Aligning the flight to the promotional period is another calendar join that frequently slips.
What should be decided in advance?
Flight length, rotation cadence, and what would extend or cut it. The last one matters because in-flight decisions get made anyway, and making them against a pre-agreed criterion is better than making them on a mid-flight read.
How should length be reported?
As delivered days by store, because stores enter and leave. A national flight length is a plan; delivered days per store is what happened.
Frequently asked questions
Is there a minimum useful flight length?
Long enough for a typical shopper to visit at least twice, which depends on the visit frequency of the stores bought. Shorter than that and the campaign is reaching each shopper roughly once, which suits some objectives and not most.
Does a longer flight always reach more people?
It reaches more of the infrequent visitors, with diminishing returns as the frequent ones are saturated. The reach curve flattens and the flattening point is the practical answer to how long is long enough.
Should flights be continuous or bursts?
Bursts concentrate weight and suit launches and promotions; continuity suits categories bought regularly. The channel supports both and the choice should follow the objective rather than a convention.
How does frequency accumulate here?
Quickly, because the same shopper returns often. That is the channel's structural advantage for frequency and the reason creative rotation matters more here than in low-frequency media.
What if the store list changes mid-flight?
Delivered days by store is the honest reporting, and the plan's reach estimate should be updated. A store added late has not delivered the full flight.
Does seasonality affect flight length?
It affects what length is worth buying rather than the arithmetic of reach. A seasonal category has a window and the flight should fit inside it.
How long before a result can be measured?
Long enough for the effect to accumulate and for the measurement to have power, which usually means the full flight plus a post period. Reading a result mid-flight is reading noise.
Is a very long always-on presence wasteful?
Only if the creative is not rotated and the store list is not maintained. Both are manageable and both are frequently neglected.
What determines the answer more than anything?
Visit frequency in the stores you bought. Everything else in flight planning follows from it. General out-of-home planning practice is discussed by bodies such as OAAA.
### How should a flight be reviewed mid-way?
On delivery rather than on effect. Checking that plays, stores and uptime are tracking the plan is useful mid-flight; reading a sales effect from half a flight is reading noise.
If delivery is short, there is time to remedy it. If it is on track, the effect question waits for the agreed window.
Does a longer flight always cost more?
In media, generally, and the cost per unit of reach can fall as the flight lengthens because more distinct shoppers are reached. Comparing flights on cost per reached shopper rather than on total cost is the more useful frame.
### How should flights be spaced?
With enough gap that a burst is distinguishable from continuity, if bursts are the strategy. Flights spaced closely enough to overlap in effect are effectively an always-on plan with variable weight.
Where the objective is seasonal, the spacing follows the season. Where it is continuous, the question is really about weight rather than about flighting.
Does a gap between flights lose accumulated effect?
Some decay is expected and its rate depends on the category and the message. Measuring during a gap is one of the few ways to observe it, and almost nobody does.
Should flight length differ by store cluster?
It can, where clusters have different visit frequencies. A cluster with slower footfall may need a longer flight for the same reach.
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