Some pleasing aviation arithmetic

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In an industry characterised by operational complexity, intensive optimisation and attention to every conceivable detail, the numbers can get very complex very quickly.

But sometimes, simple numbers provide powerful results. Today’s article is about three of these:

1. Why is daily service so much better than five-days-a-week?

2. Why is 3-3-3 abreast (pictured above) a more common aircraft configuration than 2-5-2 abreast?

3. Why is carry-on baggage a bigger issue for continent- and region-sized low-cost carriers than long-range full-service airline brands?

Now read on…

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1. Why is daily service so much better than five-days-a-week?

Imagine an airline flying a route once a week. Say out on Monday and back on Monday. Passengers have one choice – out Mon-back Mon.

Suppose they double the frequency to twice-weekly. Say out Mon and Wed, back Mon and Wed. Now passengers have four choices – out Mon-back Mon, out Mon-back Wed, out Wed-back Mon, out Wed-back Wed.

Three frequencies give nine combinations, four frequencies 16. Five frequencies give 25 choices and seven, or daily frequency, gives 49.

Moving from one weekly frequency to two doubles the cost commitment to a route but quadruples customer choice. A fine return in many cases.

In the same way, increasing frequency from five-weekly to daily doubles consumer choice for a 40% cost penalty. This is why daily service is so much better than five-days a week.

Even if flights are not so busy on two or three of those days, airlines might be able to charge more on the flights that are, covering the cost and maybe even earning a surplus.

Eventually this strategy runs out of puff in all but a few longhaul markets. But there are plenty of short-range services where high frequency is prized. on short business trips for example people will value the chance to come back on the same day they arrive.

Double-daily service gives 196 combinations, four-times daily. Triple-daily gives 441 and quadrule-daily a whopping 784.

The marginal extra flight a day runs into returns that are increasing but diminishing though. Double-daily services offer four-times the choice of daily. But triple-daily offer 2.25-times as much choice as double-daily. Quadruple-daily offers 1.78-times the choice of triple-daily.

On the day this article is published BA is scheduled to fly nine times a day from London Heathrow to New York. Add three codeshares with American Airlines and the frequency is an enormous twelve flights a day, counting both JFK and Newark airports as New York.

Yankee competitor United Airlines is scheduled to operate six flights on the route and groovy-funky Virgin Atlantic offers four flights. That is a considerable choice.

Emirates out of Dubai to London is another example of a high-frequency long-ish range route.

On London to Los Angeles, another prime route, the BA-AA pair offers four flights a day. When I flew to Dallas there was a choice of four AA and one BA flight.

On some routes, choice looks high at first glance but in practice is a bit more limited.

BA offer an early evening and late night departure from London to Singapore, for instance. But both of the return flights are late night departures arriving at zero dark hundred hours.

This type of overnight scheduling was considered desirable in a business travel heavy world. Long-range daylight flights are sometimes known as the Chairman’s Special because only the Chairman dare take them.

As the airline industry moves to on-board connectivity I think we will eventually, over decades, start to see more daylight services. Many workers and their bosses will consider a short day of good work better than a long day of poor work following a red-eye.

2. Why is 3-3-3 abreast a more common aircraft configuration than 2-5-2 abreast?