Tougher security regulations in the U.S. than in other parts of the world have mostly prevented the deployment of unassisted self bag-drop machines in the country's airports. But though those regulations remain in place, U.S. airports and airlines are now increasingly exploring self bag-drop technologies and preparing for the possibility of a rollout.

"We want the most efficient throughput that we can have," said Stu Williams, senior vice president for special projects at Denver Airport, which in September ordered 176 machines from the German vendor Materna that are capable of self bag drop.

The order, which to date is the largest of its kind in the world, means that by 2020 every bag-drop location at the airport will be equipped with self-check capability.

"The whole philosophy behind this is to provide an efficient and customer-friendly service," Williams said.

According to a study released in November by the aviation industry IT company SITA, which is also a vendor of self bag-drop machines, 45% of airlines globally offer unassisted bag drop. In such cases, passengers' identities are typically verified by an agent as they pass through a line to access the bag-drop machines.

Once at a machine, however, passengers can drop and weigh their bags, scan their bag tags and boarding passes, then leave their bags to be routed to their flight, all without further agent contact.

Some machines are also equipped to accept payment for bag fees or for oversize bags. The newest machines also offer biometric identity capabilities, paving the way for the possibility of check-in and bag check without any agent contact at all.

Penetration of self bag-drop machines is high in Europe, Asia and Canada in particular, according to vendors and IATA manager of facilitation Hasse Joergensen.

When deployed, such machines can be time-savers. British discount airline EasyJet, for example, introduced 48 automated bag-drop machines at London Gatwick in 2016 and said that they reduced line lengths by more than half. Gary McDonald, Materna's president for North America, said the average bag-drop time for the 96 machines the company has deployed at Gatwick is 51 seconds.

For airlines, self bag drop offers other benefits, as well. McDonald said that at Gatwick one agent can monitor 12 to 14 machines, making for substantial cost savings in comparison with traditional agent-aided bag check.

In the U.S., however, TSA rules require that an agent manually verify that the person physically checking bags is the ticketed passenger he or she is purporting to be.

The TSA declined to comment on its bag-drop rules for this report. There are signs, however, that the rule could eventually loosen, perhaps in conjunction with more widespread deployment of biometric identification solutions at airports, a process that U.S. Customs and Border Protection (CBP) is actively facilitating as it works to fulfill a mandate from Congress to collect biometric records on all foreign nationals departing the U.S.

Recently, the TSA also pledged to speed biometric development, and in October, the agency released a road map for biometric expansion.

In the meantime, airlines and airports have begun trial programs featuring self bag drop.

Delta, American and United, for example, have undertaken trials of self bag check at Minneapolis-St. Paul Airport. Alaska has tested the technology in Los Angeles. Delta is deploying biometric self bag check at Atlanta's Hartsfield-Jackson Airport as part of an end-to-end biometric journey it is offering flyers at the airport's international Terminal F. And Miami Airport is currently partnering with American on a self bag-check trial.

Maurice Jenkins, Miami Airport's head of information systems, said, "We are looking at whether there is an efficiency to be gained." He added that preliminary data has suggested the answer is yes.

JetBlue, meanwhile, will begin testing biometric self bag drop on international flights in early January at two machines in Terminal 5 of New York's JFK Airport. The machines will use facial recognition cameras to verify flyers' identities against data held by CBP.

For the trial, an agent will also be at each machine in order to comply with TSA rules, said Caryl Spoden, JetBlue's director of customer experience. The TSA will be reviewing the results of the trial.

"We have to essentially prove to them that this method is just as secure, if not more secure, than the current method," Spoden said.

JetBlue almost surely won't be the last U.S. carrier or airport to trial biometric bag drop.

Edward Bauer, senior director of North American airports for SITA, said the company is seeing increased interest from U.S. airports wanting to launch trials of various types of self bag-drop technology. But he expects the momentum to be toward the biometric options as opposed to those that don't offer identity confirmation.

"Certainly, that is the trend the industry is going to move toward," Bauer said. "Some airports will deploy agent verification of IDs as a possible interim solution."

In Denver, airport officials decided to order hybrid bag-drop machines in order to both accommodate the existing TSA regulatory regime and to be prepared for a potential future in the U.S. in which unassisted self bag drop, with and without biometric facial recognition, is common.

The 176 Materna machines being installed at Denver Airport are part of a broader overhaul of the airport's central Jeppesen Terminal. Their addition, Williams said, will provide individual airlines the flexibility to handle bag check as they choose.

"The whole philosophy behind this is to provide an efficient and customer-friendly service, whether you are getting tickets or dropping your bag," Williams said. "And even though this hybrid system is new, it's efficient with time. It's efficient with airlines as far as with their staffing needs and, obviously, the flexibility."