MileagePlus members can get Clear for $119 per year -- not trivial, but a significant deal over the usual $179. Most United credit card holders, as well as Premium Silver, Gold and Platinum members, will pay $109. Jetsetters with a Global Services or Premier 1K membership, meanwhile, will have access for free.

The arrangement follows United making a "strategic equity investment" in Clear to foster the company's growth.

As with earlier biometric initiatives at airports, this is all about the appeal of convenience -- you can spend less time wading through security and more time at the gate. United can process its passengers more efficiently, for that matter, with shorter lines and fewer flights behind schedule. Privacy and security remain issues, though. While Clear and United stress that the technology is "secure and seamless," it's still the case that you're trusting your sensitive biometric info to a third party. You're counting on Clear protecting the data against breaches and unwarranted law enforcement requests, and those are large promises to make.