An IATA official has recently been quoted as saying that, 'A slot management system is indicative of a failure of governments or airports to invest in adequate infrastructure to keep pace with airline demand.'

Should governments and airports always invest to meet airline demand?

Consider the issue of de-peaking. Until recently, airlines worked on a hub-and-spoke basis, scheduling large numbers of flights in and out of hub airports in 3-4 waves each day - early morning, lunch time, late afternoon, and evening. They all connected with each other and then flew off again.

Surprise, surprise - this caused overloading of facilities at peak times and under-utilisation out of those peaks. What did airlines do? Why, they de-peaked at key airports.

Aircraft still came into hub airports in those waves, but their departure was sometimes re-scheduled so that the peak load on check-in and baggage staff was reduced.

So - by IATA's argument - airports should have invested in capacity for the peak caused by the historic hub-and-spoke operation when that became fashionable. They would, of course, then have been left high and dry by the subsequent de-peaking, having invested in long-life assets which the users no longer wanted!

Consider the fact that aircraft are mobile assets and airports are not. Some airlines will - rightly - try a route for a season or two to see if they can make money out of it. If they can't, they pull out. So what should the airport do? How much should they invest for an operation which might not last beyond tomorrow?

And consider the impact of frequent flights by small aircraft or less frequent ones by larger aircraft (an issue studied, incidentally, in ACRP Report 31, available on the TRB web-site).

If an airline schedules a 50-seat plane every half hour instead of a 100-seat plane every hour, it takes up twice as many slots for the same number of passengers. OK, on this one you could argue passenger convenience - all other things being equal, people prefer frequency. But is it really worth it - is it a good use of scarce runway and slot capacity?

Is it worth increasing capacity - as IATA suggests - for this kind of thing?

To me, the killer argument here is that of San Diego. This is the busiest single runway airport in the United States, handling 17 million passengers a year. It has spent much time, money and effort looking for ways to increase capacity because, it is said, it's full.

But look across the Atlantic, to Gatwick - the busiest single runway airport in the world, handling exactly twice as many passengers! The key difference is aircraft size.

The predict and provide policy - predicting demand then providing infrastructure to meet it - has been discarded in other areas. How much does IATA need to catch up with this? Because another leading IATA manager has been quoted as saying that airports should use their charging system to re-distribute traffic - a peak charge signals the cost of the additional infrastructure needed for the peak.

A colleague recently moved from the aviation industry to the rail industry. The key difference he noticed was that the former was always planning for growth, whereas the rail industry was planning for a steady state.

This led me to wonder what the aviation industry would look like if it wasn't always growing! I have as yet come to no conclusions, but there was an interesting presentation at the TRB Annual Meeting in January which showed that air passenger growth might be slowing significantly.

And, logically, it cannot continue. In my lifetime, fares have continued to drop in real terms, and this has led to the growth in air travel we have seen. Can this go on?

Your thoughts would be appreciated!