I have always known that the acronym for an official Notice to Airmen is NOTAM.

I've just come across the acronym for notices specifically about snow on airfields - the Snow Notice to Airmen. It's a SNOWTAM.

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!

A colleague has made the interesting suggestion that it may be time to rethink how classes of service on trains are described or branded. He comments that the standard of accommodation on many first class train services is similar to premium economy on an aircraft.

He also speculated that occupancy might rise if the service was branded Premium or Business Class, since most companies have a travel policy which is aimed at finding the best business class service.

In addition, he raises the question of airlines which offer a rail service as a complimentary feeder service between airport and specific domestic destinations for certain fare types. Should this be a premium rail service for a premium air traveler? This is likely to depend on the traveler profile and the policy of the individual carrier.

Fascinating stuff!

As an economist, I approve of the concept of providing a number of classes and therefore a number of prices. It helps to maximise revenue, and it improves customer choice.

However, one needs to be culturally aware - in particular, of what to call the two classes.

In Japanese trains, there is Ordinary Class and Green Class. On some, you pay less if you have to stand: you can also have a compartment in Green Class which costs more than the ordinary Green Class, effectively making 4 classes.

On the Dubai Metro there is Gold and Silver Class.

I'm glad the UK rail network changed form Second Class to Standard Class: the argument was that you shouldn't be calling 80% of your passengers "second class"!

Heathrow Express had a big debate about what to call its classes: they decided on First and Express (and the term 'Express' was my idea!). First and Business was decided against, on the grounds that lots of people weren't travelling first class and were not travelling on business!

Amtrak provides coach and business class on the Acela Regional trains, and business and first on the Acela Express.

I was fascinated to learn recently about the Club Car on New Jersey Transit. A group of people pay to have a dedicated car attached to one peak train each way: the car has more comfortable seating and more leg-room than the average commuter car. Passengers pay their fare to NJT and a supplement for travel in the Club Car. You can pay by the day or for a month.

Moving on to the second point, I'm pretty sure that those airlines which offer complimentary rail travel in conjunction with a flight only offer first class. I also understand that the take-up of rail is good - at one stage, people like Virgin Atlantic and Emirates were offering their preferred passengers a choice of a limo or Gatwick Express to London, and most chose the train because of its reliability.

On both the Stuttgart and Cologne to Frankfurt and the Brussels Midi - Paris CDG air-rail code shares, all rail travel is in first class.

One reason for the unpopularity of the short-lived code-share between SN-Brussels and Thalys on the Paris Gare du Nord - Brussels Airport sector was that rail travel was in Confort-2 class and not Confort-1.

I'm not sure what happens on other rail-air code-shares.

It was also interesting to see that American Airlines now offer what they call Express Seats! Customers can buy seats in the first few rows of Coach, including bulkhead seats. In addition to sitting in the front of the main cabin, the Express Seats option also includes being in Group 1 of General Boarding, providing the benefit of being among the first Coach customers to board the plane. Express Seats can only be purchased at airport Self-Service Check-In machines between 24 hours and 50 minutes before flight departure, on flights within the United States, Puerto Rico and the U.S. Virgin Islands.

This has been done by Ryanair for a while - passengers can pay a priority boarding fee to be among the first to board - and therefore to have the best choice of seat. I do not know whether there is any limit on the number sold - could everyone buy priority boarding?

So what do you think? Should first class rail be re-branded? To what?

I understand that 15% of the capacity at Sydney Kingsford Smith airport is taken up with the shuttle to Canberra. There are flights every 40 minutes on this 250 km sector.

The airport is capacity constrained, and plans for a replacement or for additional capacity are not close to fruition.

A high speed rail link sounds like a good idea, for all sorts of reasons.

Does anyone know the economics of those flights? A 250 km sector is pretty expensive to fly!

I've just flown from London to Hong Kong and back on Air New Zealand, and thought I would record my experiences.

The first shock was that I couldn't check-in on-line! How many airlines today do not offer this?

Check-in at Heathrow Terminal 1 was a bit of a scrum, because so many people were travelling with a lot of heavy luggage. Several people were unpacking and re-packing to try to get individual bag-weights right - at Terminal 4, there's a dedicated area with scales and tables where you can do this.

It was a hot day, so some people had come lightly dressed - and to reduce the weight in their bags, were putting extra clothes on!

I just had one hold bag, so I was hooked out of the economy class queue and taken to the business class check-in. Thanks for that!

My flight was due to leave Heathrow at 21:05. On my boarding pass and on the flight information displays (FIDS), it said boarding time was 19:35, which I though a bit early. At 19:38, the FIDS changed to "Please wait" and at 19:50, the gate number was displayed. I actually boarded at 20:42!

I felt the crew were a bit authoritarian in style.

BA style is for the pilot to ask cabin crew to, "Switch doors to automatic and cross-check": the ANZ crew were instructed to, "Arm your doors".

I was whinged at twice by the crew for opening the blind to look at the spectacular scenery. Hey, guys, that's why I book a window seat! And before you respond, the people beside me were awake.

The in-flight entertainment required numerous re-sets: this even affected the cabin reading lights.

The moving map showed Lithuania and Latvia as fixed points rather than real countries, so at one stage a compass on the map showed Latvia to the north-west and Riga, its capital, to the north!

The display was complex and in both English and Cantonese, so I found it quite difficult to follow. By the time the English version of the local map came round, the place I'd seen and wanted to identify was far behind!

The use on the moving map of just metric measurements for speed and height (10882 metres instead of 36,000 feet), and mach numbers for speed, seemed slightly odd. I thought aviation standard was Imperial? And who knows what a mach number is anyway?

The pilot announced the distance to Hong Kong in nautical miles at one point, just to add to the confusion!

Having announcements repeated on the in-flight entertainment (as a note at the top of the screens) was, I thought, a good idea - especially the "Fasten seat belts" message.

We flew through a thunderstorm over the Netherlands and Germany - quite spectacular!

My evening meal had no pasta starter but two helpings of dessert! No menus were supplied, but the cabin crew announced the choices over the public address system.

On the flight back, I was annoyed to find that the in-town check-in at Central Station closed at 17:00: I was told that it was the same at Kowloon at the airport. A pain, for an early morning flight.

And as we arrived at Heathrow, we were asked to fold blankets and put them in the overhead bins, ensure that the bins were left open after we'd taken our belongings out, put the window blinds down to keep the plane cool while it was awaiting its return flight, and watch that we didn't mark the business-class seats - the ottomans - with our rolling cases as we went past!

I expect that the last person out was also asked to switch off the lights and lock the doors!

One was invited to give feedback by email (and New Zealand residents who were members of their frequent flier club would be entered into a quarterly prize draw for 500 points if they did so): the survey is on www.airnzmyvoice.co.nz.

You may deduce that my feedback is not particularly complimentary!