Until recently the only thing apart from love that money could not buy was a guaranteed place at the front of an airport security queue. That is changing, as an additional 500 US air passengers a day agree to hand over a $100 (£50) annual fee, plus their fingerprints and iris scans, for the right to become “registered travellers” in private programmes supervised by the Department of Homeland Security.

Once the authorities have run an applicant’s background checks to ensure he or she is not a threat to airline security, the successful RT receives a credit card-style pass containing biometric information and the privilege of joining specially designated fast lanes at a growing number of US airports. The market leader, Verified Identity Pass (VIP), has received about 100,000 applications, of which 75,000 have been approved.

It is early days, so even RTs must for the time being share with the common herd the routine indignities of juggling shoes, jackets, toiletries and laptops as they head for the scanners.

For now, the practical benefit of the RT card appears to be as a licence to queue-jump. “Basically it puts you at the head of the line,” says Cindy Rosenthal of VIP, which offers RT cards under the Clear brand. “But we don’t want to use that term.”

The idea for Clear and other emerging RT brands was spawned by the perceived need for tighter airport security following the September 11 2001 attacks on the US. The homeland security department, created five years ago, decided to bring the private sector into efforts to break the emerging security logjams at US airports.

Private companies would not only take on the role of running RT programmes, in co-operation with homeland security’s Transportation Security Administration (TSA); they would also provide the investment for developing more sophisticated airport security technologies.

Steven Brill, Clear’s founder and CEO, spotted a market opportunity. The former journalist, legal commentator and founder  of Court TV wrote in his 2003 book After, describing how the US coped with the trauma of 9/11, that if confronting the threat posed by terrorists became too onerous in terms of freedom, cost and convenience, the terrorists would have won the battle.

“Somehow, we have to find common-sense solutions that don’t make everyone a suspect and create security bottlenecks everywhere we go,” he tells would-be RTs. “To be blunt, that means we need a fair, sensible way not to treat everyone the same when it comes to terrorism protection.”

So what do he and other providers offer for their money? A one-off $28 fee goes to the federal authorities to carry out the background checks. The remaining $100 annual charge goes to provide fast-track lanes at 17 US airports, with eight more due to come on stream this year. Clear also offers an on-site “concierge” service to help with those awkward shoe and jacket checks.

Similar RT services are offered by Flo Corp, partnered with companies that include JPMorgan, Microsoft and Vigilant Solutions.

Presumably, as more passengers sign up (the programme is currently limited to US citizens and resident aliens), all queues will lengthen. Not so, says Clear’s Ms Rosenthal. “If we started taking 25 per cent of the traffic but only using 10 per cent of the lanes, other people would get through quicker.”

The RT providers also say they are involved in technological innovation that will benefit all travellers. One of Clear’s biggest investors is GE, a leader in security technology, which has rolled out a machine that can simultaneously scan irises and shoes.

Clear has also offered a $500,000 prize for the best innovation in fast-lane technology that gets approval from the TSA.

The US fast-track model has excited interest elsewhere, and GE scanners not yet approved for permanent use in the US are already being offered in Europe to help speed frequent flyers on their way. Amsterdam hosted a registered traveller forum last month and the European Commission in February raised the possibility of granting RT status to third-country nationals.

Civil libertarians worried about handing over their biometric details – despite the assurances of the RT providers that their movements will not be tracked – and those too mean to cough up $128 need not feel left out.

The TSA is introducing a system that allows air travellers to “self-select” their profiles to speed processing times. Passengers will be invited to choose between three separate security queues set aside for Expert, Casual and Family/Special Assistance travellers.

The TSA says the pilot programme has proved hugely popular, and said this month it was extending it to include eight US airports by the end of April. But expect confusion when granny takes a trip.