“I asked our head of flight operations to select a dozen of our pilots who were well-liked by everyone,” Kirby said in a recent interview with McKinsey and Company. The leader of the $31.7 billion airline giant explained that after being selected for an interview, part of whether or not they move forward depends on if they’d be good company. 

“I told this group of pilots, ‘Your job is just to assess: Is this interviewee someone I would like to take a four-day trip with? And if you say no, then they’re out. You get a veto vote,’” the CEO continued. 

“The idea is to pick people who care about others, who you want to hang out with, who you want to be with.”

The competition is fierce for jobs at United Airlines

The hiring hack is just one layer of the competitive process to land a job at United Airlines; a spokesperson tells Fortune that it’s part of the larger process of hiring pilots, aside from the standards set by the business and the Federal Aviation Administration (FAA). 

And this vibe test could serve as one way to separate the best talent from the rest of the pack. 

Kirby said that whenever they open flight attendant hiring for around 3,000 positions, the company receives 75,000 eager applicants within a matter of hours—hovering around a 4% acceptance rate. 

He also reasoned that the business is “one of the few places left” where workers without a college diploma can work in a multitude of roles—from flight attendants and tech ops, to ramp and gate agents—and can still earn six-figure incomes. 

“So for us, the question is: How do you find people who have the right mentality and customer service attitude?” Kirby said. “We can train them to do the jobs, but how do you build a process to pick the right people and keep them excited?”

The CEOs have their own interview tests—from the car commute to the dinner table

Duolingo CEO Luis von Ahn doesn’t even wait until a candidate arrives to start his assessment. The moment a job contender gets into the car, the hiring process is already underway; Ahn says how a candidate treats their driver on the ride to the office plays a part in whether they get the role. And he’ll even slip the taxi drivers some extra money to weigh in on if they’re worth hiring. 

The billionaire cofounder recounted a time when Duolingo had been on the hunt for a chief financial officer for a year. Ahn really liked one candidate who had an impressive résumé, but he turned down the applicant after learning they were “pretty mean” to their driver from the airport to the office. Similar to Kirby, Ahn believes personality can make or break a hiring decision. 

“Our belief is if they’re going to be mean to the driver, they’re probably going to be mean to other people, particularly people under them,” Ahn said on The Burnouts podcast earlier this year. 

Twilio CEO Khozema Shipchandler may put the company’s senior job candidates through multiple rounds of interviews, but their success could hinge on one single question. After having a 45 minute dinner with the interviewees, the leader of the cloud communications company will pose a question back: “Do you have any questions for me?” If they pass on the opportunity or offer a blank stare, their odds of landing the gig drops instantly. 

“The number one red flag for me is when someone doesn’t ask questions towards the end of an interview,” Shipchandler told Fortune last year. “I think that’s a pretty significant mark against them being curious about what they’re interviewing, the company, the way we might work together, chemistry, culture, all of those things. That’s a pretty big red flag.”

Former Indeed CEO Chris Hyams has also stuck behind one pivotal interview question in assessing more than 3,000 candidates over the past 15 years. Instead of testing their personality, he had tried to gauge their decision-making skills through their responses. 

“It might seem strange, but I ask everyone, ‘Do you have an iPhone or an Android, and why?’” Hyams told Fortune last year. There is no “wrong answer,” but the leader uses it as an icebreaker that opens up conversation on their passions and product sensibilities, also engaging their reasoning skills. 

“And it’s actually a long 15-minute series of back-and-forth on this, where I get to learn a little bit about the human being, and about how they make decisions,” Hyams continued.