Delays are among the most annoying things one can encounter when taking a trip. The process of flying already provides anxiety for some people that don’t feel comfortable in the air for long periods of time. Potential delays just make it worse for everyone. It changes the plans of one’s trip as they will likely get to their destination later than expected. Some delays don’t even have a timetable expected as folks will fear the uncertainty of their flying situation waiting on it to be resolved. Many fliers don’t even know what exactly causes their delays when it hits them.

We will look at some of the most popular instances of why flights are delayed and some of the stranger ones. Both sides have been real things that prevented airplanes from taking off and/or landing at the estimated time. The common reasons are things that happen in everyday life that leads to the flights being delayed with less of a surprise. These are the ones that travelers must accept as they happen to a lot of people. The less obvious reasons will likely cause more frustration when impacting your trip. These are the fifteen most common reasons for flight delays along with five not-so-common reasons.

20 Common: Busy airport congestion

Popular airports sometimes have the issue of congestion, causing delays. Many flights will see a delay due to an airplane being behind or ahead of yours. It has become a common reason for delays specifically at the New York City airports of JFK and LaGuardia.

The delays here will be even more frustrating than the average one. It usually takes place when the plane has landed or is about to take off. Passengers are stuck on the plane wondering when they will be able to get in the air or move to their terminal to get off the plane.

19 Common: Wait for crew members

Various shifts for each airline see employees on flights rotate throughout the day when it is their time to clock out. Much like any other job, there are moments when an employee is late, or a staff is short-handed, and someone must come at the last minute to fill in.

Many flights get delayed as the airline awaits crew members to show up for the flight. The flight needs enough employees for a safe and comfortable flight experience. While annoying, these issues are often understandable as they can happen at any job. The delay dragging on is what will cause the passengers to get upset about the wait.

18 Common: Fueling

Refueling a jet can lead to a long wait if the plane needs it done before taking off. It can be as long as two hours to make sure the plane is properly fueled for a long flight. This is a more common flight delay for those on long trans-oceanic flights.

Passengers won’t find out about such a delay until getting to the airport given it is something that is usually realized at the last minute. The wait can be a pain to deal with due to the unexpected wait, but it is one delay that is for the safety of everyone involved on the flight.

17 NOT common: Rowdy passenger

All it takes is one loud person to become an issue for a flight to get disrupted. Passengers that get out of hand and cause trouble on the flight can cause it to be delayed. This is up to the discretion of the crew members on the flight and they are usually lenient.

However, the flight will be delayed if the person is going too far and refuses to stop their antics. Some flights get delayed as the crew awaits security to show up and escort the disruptive person off the plane before taking off. Many sitcoms and movies have used this situation for comedic purposes.

16 Common: Waiting for and loading cargo

Cargo used to be the main source of income for the early years of the airline industry before passengers started traveling all over the world. Many flights will still take on cargo when suppliers pay to have their items flown to the destination.

The United States Postal Service is a customer for various airlines in the country. This is a reason for some small delays as the wait is to get the cargo and load it on the plane before taking off. This sometimes means that the plane will arrive later than expected.

15 Common: Waiting for and loading bags

The combination of luggage and connecting flights can each lead to delays separately or collectively. Many connecting flights will see the wait time of luggage from one plane to another causing a delay as the employees try to make it happen in a timely fashion.

There is also the general wait time when there’s no space left in the overheard compartments on the plane for carry-on luggage. Passengers will often have to check their luggage on the plane which adds more time if there are more than a few folks with this issue. Try to pack light or check your bags before getting on the plane for the best experience.

14 Common: Air Traffic Control

There are nearly 100,000 flights crisscrossing in the United States every day in the airplane industry. Air Traffic Control is a very important part of the aviation system. If the air traffic is extremely busy at a specific time, it will cause certain flights to wait longer before taking off or landing.

Holidays or busy days are typically the times when this issue will arise to cause frequent delays for those flying. Passengers flying on a well-known busy day are advised to check flight status before flying out. Too many flights in the air at a certain time from all airlines will lead to Air Traffic Control delays.

13 NOT common: Late pilots

One of the most frustrating experiences one can have on a flight is hearing that the pilot has not shown up on time. It is quite uncommon considering a pilot is arguably the most important person for each departing flight.

However, there have been some rare instances of pilots not getting to the airport on time to start their day of work. This will lead to a delay as the airline tries desperately to figure out when the pilot will show up or if someone can fill in. Luckily, pilots are often punctual, and this is a very unlikely scenario to ever encounter.

12 Common: Catering issue

Food is an important part of many flights for all airlines. Not all flights will serve meals, but the ones that promise it can’t back out for any reason or it will lead to a negative reputation. This has led to certain food related issues causing flight delays for airlines.

Many flights will not have enough food or food options available and will require getting more options from the catering truck. There are even sometimes small issues like not enough specialized food items for vegetarians or folks with allergies. A shortage of food options is a reason for quite a few flight delays often, but these delays seem shorter than others.

11 Common: Computer glitches

Technology is an extremely important part of the world today and flying is not exempt from that. One potential glitch or technical issue can lead to a huge issue for a flight. Any glitches before a flight takes off will lead to a delay as the crew attempts to figure it out before departing.

Many instances of glitches will see the flight completely get canceled altogether with a refund or later flight time on another plane being offered. Safety is the most important thing for all airlines, and no one wants to have a dangerous moment due to ignoring potentially serious issues.

10 Common: Boarding passengers

One delay that is blamed more on the passengers than the airline employees are late boarding issues. Many people showing up at the last minute will cause the employees to get them situated before the plane takes off.

Airlines advise passengers to get to their terminal and board during the accurate time listed, but many people will show up late or just stroll in after the boarding process. Most employees will try to make sure they get to their seat if the plane has yet to take off. It can delay the flight by a few minutes as the last-minute crowd will have to get to their seat before takeoff.

9 NOT common: Overheated coffee machine

Not many people would expect coffee to be the culprit of a flight delay, but it has happened in the past. One specific instance saw a crew panic while mid-air on a flight from Washington to Munich. While making coffee for passengers, the machine overheated and would not turn off.

The flight crew was worried regarding the smoke and electrical smell causing an issue. It led to the plane landing in Boston for an astounding 16-hour delay. A tech crew checked everything on the plane, but the only issue was the coffee maker. This is an extremely rare and absurdly frustrating reason for a flight delay.

8 Common: Weight restriction

Every airplane has a Maximum Takeoff Weight number that is allowed for each flight. Each flight must be at or below the maximum weight to take off. If it goes over the weight limit, the flight is going to be delayed until the staff can figure out a solution to the problem.

This form of a delay is more common for flights to mountainous areas or areas above sea level. Certain instances will see luggage and/or passengers asked off the flight to reach the weight limit for the flight to take off. Any luggage removed will be shipped on a later flight and any passengers removed will likely be refunded or given the option for another flight.

7 Common: General aircraft preparation

Airlines pride their brands on providing a great experience for all passengers flying with them no matter how long the flight is. There are common delays with the crew just wanting to make sure the plane is in perfect condition for boarding.

Little things like making sure the plane is clean, or amenities like television screens are set up correctly, will cause short delays. These usually only last a few minutes rather than the longer delays we fret. Aircraft preparation is important for the crew members doing their jobs before allowing anyone on the plane during the boarding process.

6 Common: Security

Various security issues can cause a flight to be delayed due to internal or external reasons. Firstly, the TSA process is always hit or miss for passengers trying to get to their planes. Certain airlines will take it into account if enough people are late for the flight and will wait.

A broader example of security delays will see international flights needing to go through a potentially long process. Any flights landing in a foreign country need to adhere to various security clearances before departing again. It can be a timely process that leads to annoying delays for longer flights.

5 NOT common: Not enough toilet paper

Toilet paper is such a basic necessity that one can take for granted on a flight. However, it has been known to cause delays in the past. British Airways saw an embarrassing delay on a flight from England to Barbados. The flight was delayed for over 5 hours due to the plane not having enough toilet paper.

It is obvious that it’s an important issue to be solved before taking off. The fact that it can take such a long time for something so easily accessible is what makes it so annoying. Thankfully, the chances of this delay happening are extremely slim.

4 Common: Fog

Mother nature can be a huge pain to deal with, leading to flight delays for various reasons. One of the most common flight delay reasons is the fact that fog makes it nearly impossible for a pilot to fly the plane easily.

Many people struggle to see far in advance when walking on a foggy day. The visibility issues are maximized to a strong extent when trying to fly a plane in dense fog. Flights will get delayed for short or long times depending on the forecast if the fog appears to present an element of danger. It is an annoying yet common delay issue for flights.

3 Common: Waiting for connecting passengers

Connecting flights are a game changer that can make flying easier or more difficult. The ease of getting to your ideal destination or paying less money is worth it to most passengers. However, any potential delays on a prior flight can make it difficult to get on your connecting flight.

Many airlines will wait before taking off when knowing quite a few people from connecting flights are trying to make it. The captain often makes an announcement reminding annoyed passengers that they would likely want the same change to make their connecting flight if prior delays already set their travel time behind schedule.

2 Common: Storms

Bad weather is the most common reason for long flight delays as it is often unexpected. Storms are usually the cause of the most annoying delays due to the weather issues making it tough to take off for a safe flight.

Thunderstorms will see delays due to the heavy precipitation falling and potential lightning adding concerns for the pilot. Blizzards and snowstorms cause delays during the colder months. Many East Coast flights are delayed by full days if the snow is bad enough. Travelers are advised to avoid planning big trips during times of the years that are known for major storms.

1 NOT common: Support animal confusion

Service and emotional support animals have become important parts of the lives of many people all over the world. That has made it a tricky thing when it comes to flying. Most airlines will allow the average support animal like dogs or cats. However, there are quite a few more unique animals that help the same way.

Snakes, turkeys, spiders, ducks, pigs and panda bears have been some of the animals that people have tried to get on a plane for support. Airline employees often struggle to find the proper protocol on how to handle it. Either way, it can lead to a delay. The time spent getting the animal situated safely on the plane or getting the passenger off will lead to time adding up.

References: Accuweather, RD, Flightbucks, Cruisin Altitude