As some travelers discover the hard way and others through horror stories that circulate on social media, the degree to which a passport has to be damaged in order to still be accepted for travel will vary widely from airline to airline and even the country one plans to visit.

Last June, 25-year-old traveler Laila March had to spend £1,200 (roughly $1,600 USD) after TUI Group  (TUIFY)  denied her boarding on a booked flight from London to Cancun over what she described as a “slight mark” on the biodata page of her passport. The £1,000 (approximately $1,330 USD) she paid for her initial ticket was lost while British Airways accepted her on a same-day flight with the same passport without issue.

Related: Carnival Cruise Line shares key passport news

The latest incident occurred to Australian DJ producer Sean Ferris and his girlfriend Brooke on a Virgin Australia flight from the country to the Indonesian island of Bali.

Travelers claim they were denied boarding over ‘microscopic coffee stain’

“Virgin Australia decided that this microscopic coffee stain on Brooke’s passport made it ‘unreadable’ and denied us boarding our flight to Bali,” Ferres wrote in a Facebook  (META)  post to his 11,000 followers. “This is the same stained passport we’ve flown to 20+ counties with – including Bali TWICE.”

More on travel:

Another National Park just made it more difficult for you to visitDelta Air Lines makes a baggage change that travelers will likeUnited Airlines passenger incident triggers quick response

Ferres also attached a photo of the passport (the identifying information was censored out) with a dry water mark on the side. He said that an airline representative told them  they would be rescheduled but they ultimately had to pay for their own same-day flights — according to Ferres, this added up to over $3,000 Australian dollars ($2,055 USD) on a flight with Qantas  (QUBSF) -owned Jetstar for the two of them.

“Called the number they gave me [and got] ‘sorry, you were marked as a no show, you’ll need to pay for a new airfare,'” Ferres explained further.

Related: Get the best cruise tips, deals, and news on the ships from our expert cruiser

Want to avoid travel problems? Update your passport now

While Ferres continued the post with complaints about why we need “a flimsy ass piece of paper” in an age of facial recognition, the commenters were less sympathetic and pointed out that all airlines specify that anyone with a passport too damaged to be used can be refused boarding. 

The latter is often left to the interpretation of the individual check-in agent. Some travelers spend years traveling with a well-worn passport and never get refused while others are denied boarding over a small mark or scratch.

The main reason airlines deny boarding over a less-than-pristine passport is the fear that the person will be refused by the arrival country’s customs and the airline will be forced to cover the traveler’s return back. 

Low-cost airlines tend to deny travel over passport condition more frequently, although every airline has a written condition that this is something they reserve the right to do. As a result, the recommendation is always to replace one’s passport if there is any doubt as to its condition; the cost of doing so will always be less than rebooking a flight and hotel accommodations at the last minute.

“Passports must be kept in good condition, free of any damage beyond normal wear and tear, and material alterations,” American Airlines  (AAL) writes on its website. “You may be denied boarding if you travel with a passport that appears damaged or altered.”

Related: Veteran fund manager sees world of pain coming for stocks