Usually, retailers and restaurant operators must stay open 365 days a year to win a coveted spot at the Minneapolis-St. Paul International Airport. Except one — Chick-fil-A, the popular (and profitable) fast-food outlet on Terminal 1’s C Concourse.

The Atlanta-based restaurant chain has remained closed on Sunday for nearly 70 years, a testament to founder Truett Cathy’s “faith in God,” according to the company’s website. That’s been the case at the Twin Cities airport for the past three years, as well, despite written rules to the contrary.

Some competing eateries, which do open every day, privately grumble that Chick-fil-A gets to play by different rules in the high-stakes airport concession game.

The rules for winning space at the airport were made clear at a Metropolitan Airports Commission (MAC) meeting this week as retail and restaurant companies vied for 50 concession slots.

The request for proposals, issued by the MAC in March, states plainly that vendors must remain open 365 days a year to accommodate the 33 million travelers who use the airport annually.

Chick-fil-A was not among those competing for a spot on Monday — but its lease and others will be up for grabs in 2017.

The $6 billion restaurant chain was brought into the C Concourse food court in 2012 by concessionaire HMSHost to replace an underperforming A&W/Godfather’s Pizza outlet. The move came after McDonald’s was booted from the G Concourse by Delta Air Lines in late 2011, causing an uproar among travelers. (McDonald’s reopened on the D Concourse in late 2013.)

MAC officials thought Chick-fil-A — famous for its chicken sandwiches, waffle fries and frozen lemonade — would be a good grab-and-go substitute.

Since then, said MAC spokesman Patrick Hogan, Chick-fil-A grossed $2.2 million in sales at the airport last year, “making it the third-highest-grossing quick-service unit at the airport, behind only McDonald’s and Subway.

“So essentially, Chick-fil-A with a six-day-a-week operation is outselling nearly all other quick-service restaurants at [the airport] that are open 365 days a year,” Hogan added. “It is very popular, underpinning why it’s important to have national as well as local brands at the airport.”

‘I have to let go’

The MAC was aware of Chick-fil-A’s “national prohibition” against Sunday sales when it was first proposed, Hogan added.

“Do I particularly care about their religious philosophy [about being closed on Sunday]? It bugs me, but I have to let go of that stuff,” said MAC Chairman Dan Boivin. “The reality is, if they can generate the kind of revenue for an airport comparable to other destinations, then that’s fine with me.

“Their numbers are such that, in six days a week, they make the numbers of other concessions that are open for seven,” he added.

The late Cathy said Chick-fil-A’s closed-on-Sunday policy was “one of the best business decisions he has ever made,” according to the company. The billionaire traced his decision back to his first restaurant, the Dwarf Grill in Hapeville, Ga., where he “would not deal with money on the Lord’s Day.”

Chick-fil-A spokeswoman Brenda Morrow said that closing on Sunday is a matter of “valuing a work-life balance. Truett believed that Chick-fil-A operators and their restaurant employees should have an opportunity to rest, spend time with family and friends, and really just have a day to take care of themselves.”

Three years ago, Cathy’s son, Dan — now the company’s chairman, CEO and president — ran afoul of gay rights groups and others when he backed the “biblical definition of family” when asked about marriage equality. This prompted boycotts, and the Jim Henson Co. withdrew from a partnership to supply toys to the chain.

25 airports by 2016

Meanwhile, Chick-fil-A has grown rapidly, opening 96 restaurants nationwide last year and bringing its total store count to about 1,900. Beyond the airport location, Chick-fil-A has five other outlets in the Twin Cities area. Morrow noted that Chick-fil-A will be located in approximately 25 airports by mid-2016 and that all of those locations are closed on Sundays.

It’s unclear how the MAC will handle the Sunday issue when Chick-fil-A’s lease is up in 2017. Generally, retail and restaurant space in the airport is bid on in groups that combine strong and weak locations.

No other vendors have asked to shorten their hours at the airport, Boivin said, noting that there are plenty of other places to eat in the airport on a Sunday.

“The reality is that Chick-fil-A is a destination restaurant,” Boivin said. “People who travel ask for it.

“Personally, to me, their sandwich is a piece of chicken with a pickle on it,” he said.