If you love to travel, a passport is one of the most important documents you'll ever possess, as it allows you to visit almost any country in the world without a visa. But what if we told you that your passport could be not expired, but invalid nonetheless?

We all know that if your passport is expired, there's it can't be used to travel abroad or even board a U.S. flight that is en route to almost any other country. But what is less publicized is that every day numerous traveling Americans are dragged into a bureaucratic nightmare when they discover that their passports — despite what it says on paper — are in effect no good. It's something that Tom Ley, a writer for the website Deadspin, found out first-hand over the holidays (WARNING: Some not-safe-for-work language in that story).

Your passport may not be expired, but it could be invalid — here’s how

If you’re traveling out of the country but your passport is set to expire before you’re scheduled to return to the States — or even in a given period after you’re scheduled to return — you may not be permitted to fly, effectively nullifying your otherwise perfectly valid passport.

The moment of discovery for many fliers often involves befuddlement at the ticket counter and crushing disappointment when their flight — and elaborate plans — effectively disappear. The next step f you absolutely want to leave the same day or close to it can be painful. You may have to rush to the nearest passport processing center and stand in long lines at ungodly hours to get an emergency renewal. For anecdotal evidence about that experience, check out this NYC passport office's Yelp page.

Furthering the discomfort is the high price of a passport, which generally costs $110 for renewals and new applicants, but will likely be closer to $200 when you add processing fees for rush jobs.

While many Americans aren’t aware of this passport rule, the State Department says it is one of the most asked questions it receives. So how much time will a traveler’s passport be honored before its expiration date? The State Department says the answer depends on the country.

"Many countries in the world require your passport have at least six months validity remaining beyond your visit before they will allow you to enter,"the department says on its website. "Others only require three months of validity while still others only require your passport be valid at time of entry."

So, basically, before you pick a travel destination abroad you'd do well to research the specific passport rules of that country.

What happens if you have, say, three months before your passport expires and you realize you have a trip coming up soon to a destination that requires that your document have at least six months of validity? You may need to expedite that renewal. Here’s how to do it.

Here are the 4 ways to expedite your passport

There are generally four ways (some international airport infrastructures may technically constitute a fifth way) to expedite your passport application and approval process. All of them will require a $60 fee in addition to regular costs:

Right now or "Life or death" emergency: The State Department defines "life or death" situation as, "serious illnesses, injuries, or deaths in your immediate family that require you to travel outside the United States within 72 hours (3 business days)." The traveler must show proof of the emergency, although it doesn't define specific requirements.

Less than 2 to 3 weeks: It's a good idea to get the ball rolling by making an appointment at a passport agency or center. In addition to places like post offices, many universities have passport services.

Less than 4 to 6 weeks: You can make an appointment at a passport center or even expedite a renewal via mail.

More than 4 to 6 weeks: You can apply at a center or renew via mail, which should take between two and three weeks.

Traveling is supposed to be a time to recharge yourself or have fun. The last thing you need is to have it soured by passport red tape. So before you travel, always remember to check your passport expiration date. Bon voyage!