From the United press release:

The iPhones will enable agents to assist customers who have checked into their flights with several pre-departure actions, including printing boarding passes and baggage tags anywhere in the airport. Customer service representatives will also be able to assist customers with alternate flight options, helping employees at customer service locations provide additional attention to those with more complex needs.

Future enhancements will include tools to provide full check-in capabilities in airport lobbies and the ability to offer customers much of the same functionality as traditional airport kiosks.

Interesting that they are distributing the iPhone 6 Plus and not the iPhone 6s Plus. An inventory clearing move for Apple? Nah, silly thought on my part, really. The 6 Plus is still being made and 6,000 phones is not enough to move the needle.

[Via Daring Fireball]