The company generates more revenue per restaurant than any other fast-food chain in the US, according to QSR magazine.
Chick-fil-A's average sales per restaurant in 2015 were $3.9 million. Its fried-chicken competitor KFC sold about $1 million per restaurant that year.
The sub chain Jason's Deli ranked a distant second with $2.7 million in per-restaurant sales, followed by Whataburger and McDonald's, each with $2.5 million in per-restaurant sales.
So what is the secret to Chick-fil-A's success?
According to a new study from QSR and research firm SeeLevelHX, Chick-fil-A has the best drive-thru service of any of its competitors.
The chain scored the highest marks on employee politeness at the drive thru, according to the study, which compiled data from 2,000 visits to 15 fast-food chains.
Employees said "thank you," smiled, and had a pleasant demeanor during nine out of 10 visits.
The chain also had the second-highest rate of accuracy at the drive thru. Chick-fil-A got orders right 95% of the time, which made it second only to Carl's Jr.'s accuracy rate of 97%.
The only place where Chick-fil-A didn't rank highly was in speed of service.
The average wait time at Chick-fil-A's drive thru is 4 minutes and 16 seconds, which is about 31 seconds longer than the average drive-thru wait time.
The drive thru is an essential element to the fast-food business. It's estimated that 60% to 70% of fast-food chains' business comes through the outside car lanes.
One reason for Chick-fil-A's high scores on service is its face-to-face ordering process, in which employees stand outside and take drive-thru customers' orders using tablet computers.
That leaves less room for error and provides a more personable experience at the drive thru. It's also meant to speed up the ordering process.
The strategy was started by local Chick-fil-A operators in Houston and it's now being rolled out nationwide, according to QSR.