Why Do Flights Get Delayed? Unpacking the Common Causes

If you’ve ever found yourself stuck in an airport, anxiously checking your watch as the departure board changes to “DELAYED,” you’re not alone. Flight delays are a common frustration for travellers worldwide. While they can be annoying, understanding why they happen might help ease the frustration. Here are some of the most common reasons flights get delayed, categorized into controlled and uncontrolled delays.

Controlled Flight Delays

Controlled delays occur due to airline operations and scheduling issues that can be managed to some extent.

1. Late Arrival of Incoming Aircraft

Tight schedules mean that a late incoming flight causes a ripple effect, impacting subsequent departures. Airlines operate on interconnected schedules, where delays in one route cascade to the next. For example, if a flight from New York to Chicago arrives 45 minutes late due to air traffic congestion, the aircraft cannot be turned around promptly for its next journey. The turnaround process includes cleaning, refuelling, and security checks, which become compressed when the incoming flight is late. Additionally, crew members may reach their regulated duty limits, causing further complications. This ripple effect is especially common in hub airports, where multiple routes depend on a single aircraft’s punctuality. For example, if a flight from New York arrives 45 minutes late in Chicago due to air traffic congestion, the same aircraft cannot depart on time for its next journey to Los Angeles. In 2019, Delta Airlines reported that late arrivals from previous routes contributed to nearly 30% of their delays.

2. Commercial Operations

Delays can often result from operational challenges that aren’t directly related to weather or mechanical issues but are still important parts of airline logistics. Overbooking, for example, is a common practice where airlines sell more tickets than there are seats on the plane, anticipating that some passengers won’t show up. However, if more passengers than expected show up for the flight, airlines must handle the situation, sometimes by reassigning passengers to different flights. This can lead to delays, as seen with British Airways during a busy holiday season when they had to delay a flight from Heathrow to Paris by 40 minutes to accommodate passengers from an overbooked flight. Managing overbooking efficiently is key, but it can certainly affect the tight schedules of all passengers on board.

Another example is when a VIP or high-profile passenger is involved. Airlines sometimes delay flights to accommodate VIPs, government officials, or state delegations. A well-known case occurred at Frankfurt Airport when a state delegation caused a delay, as the airline held the flight for their arrival. While these operational adjustments are crucial for maintaining good relations or ensuring smooth travel for high-profile individuals, they can result in delays for other passengers, especially when there are tight connections.

Other logistical challenges, like last-minute crew reassignments, can also play a role in causing delays. If a crew member is suddenly unavailable (due to illness or scheduling conflicts, for example), the airline may need to reassign crew members or wait for replacements, which can take time. Similarly, issues with catering (such as last-minute catering delivery delays) or cargo loading, especially during busy periods, may also slow down departure times.

For passengers with tight layovers, these delays can be especially troublesome, as they risk missing connecting flights. Airlines do their best to minimize disruptions, but these operational hurdles are sometimes unavoidable and require careful balancing to maintain the overall efficiency and safety of the operation.

3. Engineering Checks

Routine maintenance sometimes reveals unexpected issues that require immediate attention. For instance, a Qatar Airways flight from Doha to Sydney experienced a 2-hour delay when technicians discovered a hydraulic fault during a pre-flight inspection. The airline’s engineers conducted additional diagnostics to identify the cause of the malfunction and coordinated with their maintenance hub to source a replacement part. This process involved both logistical planning and safety protocols, ensuring compliance with international aviation standards. Such maintenance-related delays are critical for preventing mid-air technical issues. In this case, although passengers faced a delay, their safety was prioritized over the schedule, a standard practice in the aviation industry.

4. Connecting Passengers

Holding flights for connecting passengers is indeed a common practice, especially at major hub airports where numerous international connections converge. Airlines weigh the potential benefits of holding a flight to accommodate passengers against the need to maintain their overall schedule. For instance, Emirates once delayed a Dubai-to-London flight by 25 minutes to ensure passengers arriving late from New York wouldn’t miss their onward connections. This decision helped prevent a cascade of missed connections for dozens of passengers, which could have led to more rebooking, long waits, and additional costs for hotel accommodations.

The decision to hold a flight for connecting passengers is typically made after careful assessment of the situation. Airlines will consider factors like the number of connecting passengers, the timing of other flights, and how the delay might affect the rest of the schedule. For example, at hub airports like Dubai International, where many passengers are connecting to international destinations, the airline may prioritize holding a flight for connecting passengers over strict departure punctuality. The rationale behind this is to minimize the ripple effects of missed connections, which can result in significant disruptions, passenger dissatisfaction, and additional logistical headaches.

However, this kind of decision involves a careful balancing act. While holding a flight can prevent the chaos of rebooking, hotel stays, and disgruntled passengers, it can also create delays for other flights, affecting crew schedules, airport operations, and even other passengers’ connections. That’s why airlines must evaluate the potential downstream impacts carefully.

In general, airlines strive to maintain a good balance between customer satisfaction and on-time performance. While on-time departure is important, airlines often recognize that keeping passengers connected, especially on long-haul international flights, is critical for minimizing disruptions and maintaining customer loyalty.

Uncontrolled Flight Delays
Uncontrolled delays occur due to external factors that airlines cannot directly control.

5. Weather Conditions

Severe weather is one of the biggest contributors to flight delays and cancellations, and it can have a significant impact on air travel. Weather conditions like heavy rain, thunderstorms, fog, snow, and strong winds can all pose risks to aviation, especially if they affect visibility, aircraft performance, or the safety of take-off and landing procedures.

Even though aircraft are built to withstand many of these weather challenges, such as flying in rain or light snow, extreme conditions can be hazardous. For example, thunderstorms can cause turbulence or lightning strikes, making flying uncomfortable or unsafe. Fog reduces visibility, which is crucial for landing, and snow or ice can make runways slippery or interfere with the aircraft’s de-icing systems. Strong winds can also affect a plane’s ability to take off or land safely.

Pilots and air traffic controllers work together to carefully assess weather conditions, using real-time weather data and forecasts to make decisions about whether a flight should proceed as scheduled or be delayed. If the weather worsens while the flight is in progress, air traffic control may reroute the plane to avoid areas with dangerous conditions, further causing delays.

In more extreme cases, such as hurricanes, blizzards, or even volcanic eruptions (which can cause ash clouds that disrupt flight paths), airports may be shut down temporarily. When this happens, airlines must reschedule flights and inform passengers of the new departure times or alternative arrangements. While these delays are often frustrating, they’re all done with passenger safety as the top priority.

6. Air Traffic Congestion at Departure Airport

Air traffic congestion is a common cause of delays, especially at major airports that handle thousands of flights each day. When there are too many planes trying to take off or land within a short time frame, air traffic controllers must carefully manage the flow of aircraft to prevent collisions and ensure smooth operations. They do this by spacing out flights, sometimes requiring planes to hold in a queue on the tarmac or circle in the air until it’s safe to land.

During peak travel seasons, such as around holidays (e.g., Thanksgiving or Christmas) or during large events (like the Super Bowl or a major international conference), airports experience even more congestion. This results in a higher volume of flights that need to be coordinated, which can cause delays. To manage this, air traffic control may implement flow control restrictions. These restrictions limit the number of flights allowed to take off or land within a certain time period, helping to alleviate the pressure on busy airports and airspace.

For example, during the summer travel season, when more people are flying for vacations, air traffic control at busy airports like New York’s JFK or Los Angeles International Airport (LAX) may issue delays to manage the high volume of incoming and outgoing flights. This can result in longer wait times for passengers, and even though it can be frustrating, these measures help ensure the safety and efficiency of the airspace. While it might mean a delay of an hour or more, it’s all about keeping things running smoothly and securely.

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7. Air Traffic Congestion at Arrival Airport

When the destination airport is overcrowded, incoming flights may have to circle in holding patterns or be diverted to alternate airports until there is a landing slot available. This congestion can be a common issue at the busiest airports, which are often major hubs like New York’s JFK, Chicago O’Hare, London Heathrow, or Tokyo Narita. These airports, with their high volume of flights, can quickly become overwhelmed, especially during peak travel times.

For example, if there’s a significant delay at an airport like JFK due to weather, air traffic, or operational issues, planes may be forced to wait in the air—often in holding patterns for 30 minutes or more—until the air traffic controllers can clear a slot for them to land. This situation can lead to a chain reaction, affecting not only the flights trying to land at that airport but also those coming into other airports, as controllers will need to adjust the flow of air traffic in surrounding airspace to accommodate the delays.

In some cases, if the airport becomes too congested, airlines may be required to divert flights to alternate airports. For instance, a flight to Heathrow might be diverted to Gatwick or another nearby airport if Heathrow’s capacity is maxed out. Once the flight lands at the alternate airport, passengers may experience delays due to the additional time spent getting re-routed, or they might have to wait for ground transportation to the original destination.

Limited runway capacity also plays a role. Some airports have only a certain number of runways or a restricted capacity for landings per hour, which can lead to more holding time. For example, an airport like LaGuardia in New York has relatively limited runway space compared to a larger airport like JFK, and during busy times, this can contribute to longer wait times for incoming flights.

These delays can ripple through the entire aviation network, affecting flights across the globe, as delays at one airport may cause backups in other cities, especially when planes are delayed in the air. Even with advanced technology and careful scheduling, air traffic congestion remains a significant challenge in keeping everything running smoothly.

8. Technical Issues

technical malfunctions right before departure can be a significant cause of flight delays. Airplanes are complex machines with many systems that need to work seamlessly for a safe and smooth flight. If a malfunction occurs in critical systems like navigation, hydraulics, or avionics, the aircraft can’t take off until the issue is resolved, ensuring passenger safety is not compromised.

For instance, a failure in the navigation system could make it impossible for the pilots to communicate accurately with air traffic control or follow flight paths, while issues with hydraulics might affect the aircraft’s control surfaces (like the ailerons or flaps), which are necessary for safe take-off and landing. Avionics issues, which include the aircraft’s communication, radar, and electronic systems, are also crucial for monitoring flight parameters and ensuring the flight proceeds safely.

When these issues are detected, the aircraft must undergo urgent repairs before it can be cleared for take-off. In some cases, the necessary repairs can be done relatively quickly, but in more severe cases, the aircraft might need to be swapped out for another one. This swap can take several hours, as it requires finding an available plane, ensuring it’s properly prepared, and completing all pre-flight checks before passengers can board.

The time needed for this process can also depend on the airport’s maintenance capabilities and available resources. At large, well-equipped airports, this process might be faster, but in smaller or busier airports, delays can be longer, especially if there are no spare aircraft readily available or if the repairs are more complex.

While these types of delays are frustrating for passengers, airlines prioritize safety, and addressing these technical malfunctions is crucial to ensure that the flight can be completed without further risk.

9. Security Issues

Security concerns, like unattended baggage, can create significant disruptions, especially in airports where the safety of passengers is the top priority. In the case of the Lufthansa flight from Frankfurt to New York in 2022, an unattended bag was discovered in the terminal, triggering a security response that led to an evacuation.

When an item is left unattended in a high-traffic area, airport security has to assume the worst-case scenario: the bag could contain dangerous materials or be part of a larger threat. As a result, security protocols require immediate action. In this situation, the terminal would have been evacuated to ensure the safety of everyone nearby. Bomb squads and other specialized teams are typically called in to investigate such situations.

This process can take hours, especially if authorities need to carefully inspect the area and the item in question. Even though it turned out to be a false alarm, the delay can have a ripple effect on flight schedules. In this case, the Lufthansa flight to New York was delayed by two hours, as other operations were put on hold during the investigation.

In addition to delays like this, the incident also causes anxiety for passengers, who may have to go through additional checks or re-scheduling. While these disruptions are often inconvenient, they are an essential part of maintaining safety in the aviation industry, ensuring that every precaution is taken to avoid potential threats.

10. Immigration Issues (Baggage Offload of a Passenger)

issues related to immigration, documentation, or security checks can cause significant delays for flights, and there are strict protocols in place to ensure passenger and baggage security.

If a passenger fails to clear immigration procedures or is denied boarding due to visa issues, the airline has to follow standard procedures to remove their baggage from the aircraft. This is done to prevent any unattended baggage from being transported, which could pose a security threat. The process of locating and offloading the baggage, especially if it has already been loaded onto the plane, can take time and delay the departure.

In addition to visa issues, passengers may encounter other problems that can result in delays at the boarding gate. For example, discrepancies in travel documentation (such as mismatched names on tickets and passports or expired visas) can prevent a passenger from boarding. If these issues arise at the gate, the airline may need to resolve them before allowing the passenger to board, which can be time-consuming.

Customs violations or concerns about the contents of a passenger’s baggage might also lead to further checks and delays. Sometimes, last-minute security procedures, such as random additional screenings or additional questions from customs or security officers, can also add unexpected delays to the process. If an issue arises that requires further investigation, the airline might have to delay the flight while resolving the matter.

All these steps are essential to ensure compliance with international regulations, security protocols, and safety standards. While they might be inconvenient for passengers, these delays are necessary to maintain security and prevent any potential issues during the flight.

How to Handle a Flight Delay
While flight delays are often out of your control, there are a few things you can do to manage them:

• Stay Updated: Check your airline’s app or website for real-time updates and sign up for notifications.
• Know Your Rights: Some delays may entitle you to compensation, meals, or accommodation, depending on the airline and regulations in the region.
• Have a Backup Plan: If possible, look for alternative routes or flights in case of prolonged delays or cancellations.
• Stay Calm: Travel delays are frustrating, but a positive attitude can help make the experience less stressful. Keeping yourself entertained and making use of airport amenities can help pass the time more comfortably.

Understanding why flight delays happen won’t necessarily make them disappear, but it can help travellers be more prepared and patient. The next time your flight is delayed, remember—it’s all part of the adventure of air travel!