Reducing the load helps smooth out the system

I’ve been posting some comments on a couple of stories from Dan Webb’s ‘Things in the Sky’ blog. He’s noted that the transport statistics for August 2008 show the on-time arrivals improved and mishandled baggage rates reduced and that he’s looking forward to September’s figures as there should be further impact from the capacity cuts recently introduced by the airlines.

I think the improvements we’re seeing now are related to a reduction in passenger numbers (the figures didn’t show pax volumes but Dan found them somewhere else in his second post). We should see even more improvement due to the capacity cuts.

To me, the US airport system is like juggling balls. You’re doing fine with 4 balls but when you add a 5th, you start to drop one every now and again – nothing major, just the odd “ooops” moment. The problem is when you wind up juggling 8 or more balls: it’s overload and you’re dropping lots, if not all of them.

In the US most major airports have more flights scheduled per hour than the airport can physically handle. An aircraft can’t land until the runway is clear and can’t take off until sufficient time has been allowed for wake turbulance from the aircraft that went ahead of it. So, imagine an airport that can process 60 movements per hour (landings & take offs) in good weather. Sadly, the airlines have scheduled 65 movements per hour during peak periods, meaning that airport will always have 5 movements per hour (cumulative) that are delayed at those times. These delays will increase for every hour that there are 65 movements scheduled until the peak time passes and they can start to catch up.

Now, imagine that the airport’s movement rate reduces to 40 in bad weather (increased separation between aircraft and so on). That means every hour at peak times during bad weather, 25 aircraft will be delayed. If the weather remains bad for long enough, it may take a day or two to recover.

Sound familiar?

Passenger loads play a factor in aircraft turn-around times. The more pax that have to get on & off, the longer it takes. Also, more pax usually means more luggage to unload and load. More pax & more luggage means longer on the ground.

So, if we’ve got fewer pax and they’re checking less baggage, guess what, you get faster turn arounds which leads to a better on-time rate (especially if on-time departure means pushing back from the gate on time and doesn’t include 20 minutes waiting on the ground before you leave). With prices going up and checked luggage rates being introduced, there has been a reduction in passengers which, in turn, has helped increase on-time rates and decrease lost luggage rates.

Yet another factor is the volume of luggage going through the system. After the “liquid bombers” in the UK, security introduced major restrictions on liquids, gels and such in carry on luggage. This lead to a lot of people checking their luggage and, surprise surprise, straight away there was a huge increase in the number of lost bags. A classic example of the juggler going from 4 balls to 8 and starting to lose it. Now we’re seeing a reduction in luggage with the checked luggage fees which, in turn, has helped reduce the stress on the system leading to less mishandling of luggage.

Given there’s less luggage going through the system, fewer passengers and the airlines are cutting capacity (which helps reduce scheduled movements at overloaded airports), I’m expecting that the reports for September & October will see some bigger improvements in on-time rates and much smaller mishandled baggage rates.

Now, as to the number of customer complaints – who knows where that’ll go. Until all the airlines in the US learn about customer satisfaction, I doubt we’ll ever see that number reduce significantly…

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