You may have some explaining to do if you have invalid or damaged travel documents. Avoid having to do that in a foreign language. The regulations vary by airline and country. Travel documents shouldn't expire close to the end of your trip. Should your return flight be delayed, you might need to return on a later one and you will still need unexpired documents. Check passport and visa guidelines before going to the airport. Some countries require 6 months, most EU countries 3 months, and NZ requires one month after your intended departure date. Any rips, tears or water damage could have you grounded until you can get replacement documents. Some countries require additional documents about prior travel, parental consent (when travelling with a minor), vaccination records or proof of lodging during the stay. Have you ever been delayed on a trip because of your documentation?

Many travellers may assume that as long as they're not travelling with illegal substances, their luggage will be allowed. Not so. Prohibited items can range from porn to firearms and some might surprise you. US travellers can visit the TSA website to check whether an item is forbidden. The FAA also offers guidance on dangerous goods. Although many airlines list restricted items on their website, check each country's customs websites for the latest. Some items may be legal in your country but illegal in your country of destination. Personnel may confiscate the item, detain you or deny you entry. Have you ever had a delay due to something in your or someone's luggage?

Arnold Schwarzenegger was held at Munich airport for nearly three hours for failing to declare a watch valued over $10,000 which he had planned to auction for charity. Some countries would simply "confiscate it" with no recourse. In the US, you must declare amounts of money over $10,000, or valuables that cost more than that amount. Jewellery, clothing and even electronics could fit this bill. The $10,000 limit has not changed in years and you are at the mercy of the customs officer so be nice to them. Have you ever had a dispute at the customs desk?

Prescription medication can get you in big trouble. If you plan to travel with medications, confirm the ingredients are permitted in the country you're travelling to. Some are allowed with a doctor's note, but others are completely banned. For example, pseudoephedrine, the active ingredient in over-the-counter Sudafed, is a controlled substance in Mexico. Violating the laws of your destination can have serious consequences. Check every country on your travel route – including transit countries – to make sure all your medicines are permitted. You may be able to purchase items locally after you arrive (albeit at significant cost potentially). Have you ever had "issues" due to your medications?

Here are a few more situations that can cause a delay at an airport or customs. Some are obvious to most of us but there is "one in every crowd" as they say. Which of these items has occurred on your travels?