To discourage passengers from disobeying a rule to wear masks during flights, Alaska Airlines will issue final warnings to offending customers: a yellow card.

Starting in July, flight attendants on Alaska flights will hand out formal notices to passengers — akin to a soccer referee, but in the urgent context of public health — who refuse to wear a face covering. The card comes with the threat of further sanctions, the company said. Upon review, Alaska could ban passengers who refuse to wear a mask for a period of time.

The policy comes after flight crews had to deal with some passengers who flagrantly disregarded the mask mandate, prompting the company to create the formal warning system, Alaska said in a blog post Tuesday.

Other airlines have already stripped passengers of their ability to fly. Delta Air Lines told employees last week that it has barred a handful of noncompliant passengers and will ban customers from future Delta flights if they refuse to wear a mask. And United Airlines announced last month that any passenger who refuses to wear a mask onboard will be put on an internal travel restriction list, losing their privileges for a time with the company.

Like other carriers, Alaska does list a few exemptions to the mask mandate: Children younger than 2, passengers with medical problems and passengers with disabilities that prevent wearing a face covering. Customers are permitted to temporarily remove their masks to eat or drink, the airline said.

Before passengers board Alaska flights, they will also be asked to sign a required health agreement and agree to abide by the mask policy.