Simon Calder: Heathrow's T5 is working – but do we really need T6?

Six months ago this morning, tens of thousands of passengers discovered what they had been assured would be "far and away the best airport experience in the whole of Europe" was, in fact, possibly the most expensive shambles in the world. The man who made that promise was Tony Douglas of BAA – or "formerly of BAA", as he and several senior colleagues should now be described – the man who built Heathrow Terminal 5. His customer, Willie Walsh of British Airways, was equally confident. "We're ready, so bring it on," he bragged a week before the opening of the £4.3bn facility. Even though field trials had been limited to a couple of thousand people like me pretending to be passengers, Walsh left no room for doubt that more than half of BA's Heathrow operations could be moved smoothly to the new building from day one.

Shortly after dawn, even as these gentlemen were telling reporters what a triumph the new building was, the first-ever flight from Terminal 5 departed with no luggage on board. Within two hours, Heathrow's flagship had gummed up more or less completely, and with it much of the BA operation at its home base. Over the next few days, hundreds of thousands of travellers had their journeys wrecked; rival airlines and airports watched with gleeful disbelief as BA and BAA haplessly squandered the chance to capitalise on Western Europe's biggest building project.

The expensive repercussions of this lost opportunity continue. Development on the other terminals at Heathrow has been delayed, and British Airways is running an ad campaign whose message is summed up as "T5 is better than you think".

BA's new home is, indeed, excellent – not just compared with the other, threadbare terminals at Heathrow, but with great airports around the world. It is now handling six out of seven BA flights from Heathrow, with up to 70,000 passengers a day. The airline's punctuality has improved dramatically. But congestion on the ground and in the skies continues, as the chaos on Thursday evening showed – dozens of flights were cancelled, and many more delayed, by a failure in air-traffic control.

Plenty of interested parties think the world's busiest two-runway airport should become the world's busiest three-runway airport, with a new landing strip and a sixth terminal north of the existing perimeter.

Yet the force of their arguments is dwindling with the downturn in aviation. Over at Gatwick, the cuts have already started. Four weeks from today, the final BA flight departs Newquay for Gatwick. As the airline winds down its link between Cornwall and Sussex, it has cancelled a number of departures on Tuesdays and Wednesdays next month (and on other days is offering lots of cheap £44 fares).

When the route was launched 18 months ago, it sparked protests from Greenpeace, who insisted the link was not needed. They have not had to wait long to be proved right.

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Doing the right thing comes with the job if you are a climate change project officer. Adrian Shaw holds that post with the Church of Scotland. For an Edinburgh-to- Milan trip, he meticulously planned the journey by rail: National Express to London, Eurostar to Paris and then a high-speed Artesia train from the French capital to Italy's business hub.

Shaw booked the London-Milan ticket through Rail Europe, the agency side of French Railways. Because of the disruption following the fire in the Channel Tunnel, Rail Europe urged him to cancel the trip – but would only refund the Eurostar part of the ticket, not the section from Paris to Milan. The reason: Artesia had declined to offer refunds. "As a ticket distributor, Rail Europe must abide by the terms set by the rail operators themselves," said a spokeswoman for Rail Europe. But on Thursday, after The Independent Traveller intervened, Artesia agreed to refund passengers in Shaw's position. But he is now flying to Milan – luckily on easyJet, rather than ailing Alitalia.

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Today IS World Tourism Day. To mark the event, a climate-change summit is being staged by the World Tourism Organization. Not, though, at the body's Madrid headquarters, nor in a centre of population gravity such as Delhi or Hong Kong. The conference delegates have the fortune to visit the beautifully rejuvenated Peruvian capital of Lima – for most, a flight of many hours. Good for them, bad for the planet.