Is your passport too damaged for travel? Here are 11 reasons it could be, and how to avoid them.

• Travel horror stories surrounding damaged passports have been making headlines.
• But how much damage is too much for a passport to be considered ineligible for travel?

Picture it: You're about to set off on the overseas vacation of a lifetime. With bags packed and boarding passes ready to go, you make it to the airport with plenty of time before departure.

That's when the nightmare begins. Before boarding, an airline official stops you with the bad news that you're not going anywhere. Why? Your passport is too damaged for travel.

You might assume a passport has to be ripped to shreds to be denied boarding, but that's not always the case.

A British family recently told Business Insider's Monica Humphries that they missed out on their dream holiday to Alicante, Spain, because their son's passport had a 1-centimeter rip near the binding of the first page. It would've been 19-year-old Jake Burton's first flight, his mother said.

As a result, the family spent New Year's Eve at home in the UK and lost out on £1,234, or about $1,570.

Determining if a passport is too damaged for travel often comes down to the opinion of a border authority. Still, BI asked Steve Diehl, chief corporate development officer of CIBTvisas, a global visa and passport service, to share the common reasons it happens and how to avoid it.

Page tears are just one of many reasons your passport can cause you problems at the airport

According to Diehl, there are several reasons border authorities could deny boarding to a traveler.

Besides tears on pages and covers, you may not be able to travel if you have loose or missing passport covers, hanging threads on page edges, or frayed bindings.

Diehl also said that warped or bent covers, worn or curling page edges, peeling plastic, water damage, and damage to the Radio Frequency Identification (RFID) chip could lead to issues.

Unauthorized markings or unofficial stickers could also prevent you from being able to use your passport, according to Diehl.

"Some tourist attractions will have their own 'passport stamp,' but since these are not official government agencies, they could invalidate your passport," Diehl said.

"As a rule of thumb, if you're unsure whether the passport is too damaged or not, it's better to assume it's too damaged and replace it," he added. "The last thing you want is to have a vacation ruined because border authorities declared your passport invalid due to damages."

Diehl said there are also worse things than having a passport deemed too damaged.

"Authorities may question the authenticity of a damaged passport," he said, which could cause them to "detain you or send you home."

"It's much better to play it safe," he said.

Keeping your passport in good condition is key

Diehl said that the easiest way to avoid being turned away at the airport for having a damaged passport is to keep it safe.

"Keep it out of arms reach from pets and small children. If you can, invest in a case that will protect it from spills and the elements, especially while traveling," he told BI.

He said waterproof cases are best, but travelers could also try storing their passports in Ziploc bags as a more cost-effective measure.

Depending on the destination, it may also be worth keeping photocopies of a passport handy.

"If you're traveling somewhere with inclement weather, where there may be snow or rain, make clear, colored copies of the passport as a backup in case anything should happen," Diehl said.

The worst thing that can happen is realizing a passport is damaged too late, so he also recommends inspecting a passport every couple of months to know well ahead of time whether it needs to be replaced.

Replacing a passport is also a completely different process to renewing it, he added.

"Most of the time, you can't just send it in. You'll need to go to an acceptance facility, embassy, or passport agency in person and bring the proper materials so the government can issue you a brand-new passport," he said. "If you can, schedule an appointment with the facility first so you don't have to wait in line."

In the US, current processing times for a passport replacement can take up to eight weeks, according to the US Department of State's Bureau of Consular Affairs. When expedited, the minimum processing time is two weeks.

"Getting a new passport after you damaged the last one can be a stressful process," Diehl said. "It's different and more complicated than other passport applications, and not having your passport in good shape on time could delay your travel plans."