By Richard Allen Greene BBC News Online, on a flight from Detroit to Atlanta

Richard Greene was pre-selected for a thorough search

I'm always wary of being "pre-selected". Letters telling me that I have been pre-selected, for example, generally seem to be offering me credit cards or loans I don't want.

On 11 September, I was pre-selected by Delta Airlines - for extra security.

When I checked in for an early-morning flight from Detroit to Denver - via Atlanta, Delta's main hub - everything seemed to be going smoothly.

But when I got to the metal detector, I was waved into a special queue. While my travelling companion Kevin Anderson sailed straight through, I waited with those who had been pre-selected for shoe removal, personalised scanning, and bag searches.

A friendly Transportation Security Authority officer said any of several factors would have caused Delta to single me out for extra attention: booking my flight less than 72 hours in advance (I hadn't), paying in cash (not that either), or flying one-way.

I was on a one-way flight, but so was Kevin. Maybe he has a more honest face than I do - or maybe he just slipped through.

New security agency

This level of security has become the norm following the 11 September 2001 attacks; the Transportation Security Authority itself is new, a response to the security lapses on that day.

Although a pre-selected man behind me in the queue fretted about missing his plane, most travellers and security staff treated the security precautions as routine.

When she scheduled the flight she told him there were a lot of empty seats, which was unusual - and then she said it was 11 September Debbie Hamilton, traveller

Only three years after the attacks that left nearly 3,000 people dead in New York, Washington and Pennsylvania - and on a day when cable news channels and newspapers were full of retrospectives and memorials - it was business as usual, airlines said.

American Airlines and United Airlines, the two biggest carriers in the US, both reported running normal schedules for a Saturday in September.

A spokesman for American said the airline had run reduced schedules due to lower demand on 11 September 2002 and 2003.

Delta, the third-largest airline, did not return a call seeking information, but our check-in agent in Detroit said business was about average.

Nervous stomach

Debbie Hamilton, who was flying to Atlanta with her husband for a conference, admitted that she'd had a "pit-of-the-stomach feeling" when he told her his secretary had booked them on a flight on 11 September.

The attacks have forced a complete rethink on security

"When she scheduled the flight she told him there were a lot of empty seats, which was unusual - and then she said it was 11 September," she said.

He hesitated about flying on that date, she added, but then said it was fine.

"We thought it might be the safest day to fly because of extra security, but it didn't seem like there was any at the airport," she said.

There has been no indication that al-Qaeda, which is believed to have orchestrated the 11 September attacks, plans its operations around particular dates.

The man worried about missing his plane shrugged when I asked him if he was worried about flying on 11 September.

"Nah," he said. "Next time al-Qaeda will do something different anyway."