In May, United Airlines completed the rollout of its new basic-economy fare class.

The value-minded ticket option has been the subject of controversy since it was announced late last year.

Designed to compete against the bare-bones product offerings and rock-bottom prices of ultra-low-cost carriers, the fare was targeted at a specific group of budget-conscious shoppers.

In fact, United CEO Oscar Munoz told Business Insider in an interview earlier this year that basic economy was "not for everybody" and that the airline would even prefer its customers go with the full-service fare.

For those who have fallen in with the basic-economy crowd, the restrictions are significant. While the in-flight experience is identical to United's regular-economy product, basic-economy passengers cannot preselect or upgrade their seats, are limited to a single personal item in the cabin, and must be among the last to board the aircraft.

Because of basic economy's notorious limitations, United has made effectively communicating with their passengers a priority.

"We have a lot of mechanisms, and that's why we are taking our time to roll it out, to make sure when you buy that ticket you fully well know, you ain't getting bags, you ain't sitting together with your family," Munoz said in the February interview. "We are going follow up. We are going to do all those different things."

United prompts users to acknowledge that they understand the restrictions that come with a basic economy fare. Screenshot/United

Since the interview, however, the need to make sure everyone traveling in basic economy is there of their own volition has been kicked into high gear.

The communication from United to its customers is rather extensive. Before a customer purchases the ticket on United's website, a pop-up window appears explaining basic economy's features. The pop-up remains until the customer acknowledges they understand the limitations of the fare class.

After the customer purchases the ticket, United sends a series of emails reminding them that their ticket is indeed a restricted basic-economy fare, detailing the limitations of the fare class, and saying they have 24 hours to get a refund.

The importance of these emails and reminders has become exponentially more important because of two developments.

First, United's public image has taken the beating of a lifetime over the past couple of months. Although much of it is its own doing, no airline in recent memory has had to battle such an unrelenting onslaught of bad press as United has since April. Not even General Motors' 27-million-car safety recall, Ford/Firestone's tire-separation crisis, or Volkswagen's 11-million-car emissions-cheating scandal could rival the pop culture and political furor generated by United's treatment of David Dao.

Even though United has worked hard to battle back since the scandal with a host of changes to its policies and the way it treats its customers, its public image is, at best, on thin ice. This means the last thing the Chicago-based airline needs is angry parents ranting en masse about not being able to sit with their families, or business travelers complaining about being charged an extra fee to gate-check their carry-on bags.

This brings us to the second development: Basic economy has been unexpectedly popular.

United Airlines CFO Andrew Levy said this week that 30% to 40% of the airline's economy class passengers had gone the basic route, Skift reported.

That means the scale of the operation needed to manage basic economy has increased dramatically.

But even with the reminders, some of United's passengers have used Twitter to complain that they were unaware of their ticket's limitations or didn't know they had purchased basic economy.

"We tried to make it very clear throughout the process that the customer knows they are choosing the basic-economy fare," a United spokesman told Business Insider's Cadie Thompson.

With Delta's and American's basic-economy operations up and running as well, it's most likely a matter of time before the wider flying public understands the fare class. After all, roughly 85% of United's customers fly with it once a year at most.

Until then, all United can do is fight the good fight and hope for the best.