The memo is split into four sections, covering grooming, hair, what jewellery is acceptable and clothing.
More specifically, it states that 'proper undergarments must be worn' by interviewees and current flight attendants' but must not be visible.'
Speaking with the Daily Mail, a spokesperson for Delta explained that the new additions to the memo have been outlined so that the guidelines are "more specific."
"In the interest of transparency and clarity for all prospective candidates, we are encouraging people to 'dress for success' and give a great first impression as they aspire to join the flight attendant ranks," the spokesperson said.
In addition to non-negotiable underwear, the memo lists many other quite specific guidelines for Delta employees to abide by.
"Delta Flight Attendants spend the most time with our customers and are the face of our airline," the document says. "The customer service experience begins the moment a Flight Attendant puts on their uniform."
In the subsection for hair, it states attendants must have "natural-looking" hair colour with "no stark highlights or unnatural shades."
When it comes to grooming, "personal cleanliness and hygiene must always be maintained." Eyelashes "should appear natural."
As for nail polish, strictly, "No neon colours, multi-colour, adornments, glitter, hand-painted designs or airbrushed nails permitted." Additionally, tattoos must be covered, but "bandages are not suitable for coverage of tattoos at any time."
It even included a rule regarding how you smell, stating that while "aftershave, cologne, and perfume may be used," they must be "applied lightly."
For prospective hires, the memo also outlines that on the day of your interview, you are to abstain from profanity, chewing gum and the use of phones or earbuds.
The airline's memo concludes, "[Delta flight attendants] must be passionate about enhancing each customer's experience while embodying the Delta brand.
"The customer service experience begins the moment a flight attendant puts on their uniform."
