There is more to a flight attendant greeting people boarding an airplane than being friendly or creating rapport with the airline's customers.

A flight attendant explained in a now-viral video on social media the actual reasons why they personally welcome all passengers on board a plane.

Flight attendant Kat Kamalani posted a video on TikTok explaining what they are actually doing when they are standing at the entrance of the plane greeting passengers and when they go up and down the aisle. Her video has been viewed more than 2.8 million times.

"Have you ever walked on a plane and saw the flight attendants standing right here greeting you? Or the flight attendants walking up and down the aisle. Well, I'm about to tell you what we're really doing," Kamalani asked her viewers in her video.

Kamalani said flight attendants have been trained to size up passengers as they board the plane. Flight attendants are mentally noting passengers that can help in cases of emergency.

"So when you're walking on the airplane and you see our happy, smiley face, we're actually looking you up and down and we are trying to find our ABS and what that is called is our Able-Bodied People, or person. So this is people who are going to help us in an emergency," Kamalani said.

Kamalani said attendants are looking for people that look like they were firefighters, pilots, police, nurses, military officers and doctors. She said they have been instructed to take a mental note of who and where these people are in case of an emergency.

   @katkamalani You would never guess the last part... #secretsrevealed #traveler #momsontiktok #flightcrew #travelhacks  ♬ SUNNY DAY - Matteo Rossanese     

"So in case of emergency, like a medical emergency, or we are going to land the plane, or there's a security breach, we know who's on our plane and who can help us," Kamalani said.

Apart from looking for ABPs, Kamalani said attendants are also looking for anything that "looks off." This includes possible signs of problems such as terrorism or human trafficking.

"It happens a lot in the industry and our passengers' safety is our number one priority, so we're just looking for things that look off," Kamalani said.