Simon Calder: The Man Who Pays His Way

For many Catholics in Italy and across the Continent, at least one road leads to Rome, which helps to explain the congestion on the autostrade and the vast crowds at the Pope's funeral yesterday. But for the faithful living in Britain, the prospects were trickier.

For many Catholics in Italy and across the Continent, at least one road leads to Rome, which helps to explain the congestion on the autostrade and the vast crowds at the Pope's funeral yesterday. But for the faithful living in Britain, the prospects were trickier.

Judging from the calls and e-mails I have received this week, the closure of Rome's Ciampino airport and the subsequent cancellation of dozens of flights from Britain to the Italian capital each day meant that many UK Catholics who hoped to be in Rome for the event were unable to get there. Meanwhile, another group of travellers had the opposite concern. They were weekenders who had already booked trips to Rome long before the pontiff's illness. Given the mounting chaos in the Italian capital, they wanted to postpone rather than grapple with a city in turmoil. Some city-break companies offered clients the chance to switch dates or destination, but anyone who bought a cheap flight on British Airways faced a stark choice. "Normal ticket rules apply," says BA: in other words, go as planned, or lose your cash.

Yet there is a solution: the "callable" flight - one of those rare innovations that offers a win-win-win outcome. It benefits the original traveller, the person who takes the seat, and the airline. And here's how the system works.

Suppose that some weeks ago you booked a flight to Rome for a return fare of £100. Imagine you had been offered, at the point of purchase, the following interesting proposition by the airline:

You, the traveller, give us, the airline, the right to buy your flights back. If we take up the option, we'll refund the original fare - and give you an extra £100.

The concept recognises that passengers' desires to travel differ. Anyone booking a flight for a wedding would be ill-advised to opt for a "callable" flight. But these days many of us travel frivolously. If you have booked a weekend away at a very low fare, and are not that fussed about whether you go to BIQ (the code for Biarritz) or B&Q (the do-it-yourself store), then accepting the "call" is a sensible plan.

Why should the airline make such an offer? Because it stands to make a healthy profit on the deal. A seat will be "called" only if demand for the flight in question rises unexpectedly. The surge in demand could be precipitated by an unforeseen world event, a European football match involving a British side, or something as trivial asa large short-notice stag party to Prague.

Whatever the reason, the airline will know it can re-sell the seat for a handsome sum. Judging by the fares being charged to pilgrims this week, the going rate could be £600 or more. This may look usurious, but if people are prepared to pay high fares, the airline cannot be blamed for charging what the market will bear.

The system is a humane alternative to overbooking. In a sense, the carrier is looking for volunteers to be "bumped", but is doing so in advance of the flight. The newly enriched traveller can then start looking again for flights - avoiding cities gridlocked by big events - or go out for dinner at the airline's expense.

For the technique to work, the airline must give the passenger a deadline by which time it will "call" a flight, eg three days before departure. The passenger must be allowed to cancel both halves of a return trip. And the traveller is not allowed to renege on the deal, to say: "I might have agreed potentially to sell it back, but now I've paid for my hotel and I'm looking forward to the trip." The seat will be taken away - though he or she could try to buy it back, at many times the original price.

Most of the time, the system will not come into play. Even the most efficient scheduled airline finds it difficult to fill more than 85 per cent of its seats. The only call the passenger will usually get is to board the plane. But the sooner an innovative airline brings in the system, the better: it is a form of ticket touting that is both legal and moral.

So which airline will be first to take the plunge with callable flights? Not Monarch Scheduled, judging by the response when I suggested the idea to the airline's boss, Tim Jeans: "It might work, but our systems can't cope with overlaying an 'e-bay' functionality on top of everything else."