Airlines have plenty of names for delays. You might see “late incoming aircraft”, “ATC restriction”, “ground handling” or “reactionary delay” on a message from the airline. If you are already sitting at the airport waiting to leave, though, that wording doesn’t always explain much.
These delays can happen for very different reasons. A problem with the aircraft, an air traffic control restriction, an issue on the ground or a delay earlier in the day can all affect when your flight actually leaves.
In this guide, we break down common flight delay terms and airline terminology, explain what they mean in plain English, and look at when a flight disruption may be relevant to compensation.
Aircraft rotation refers to the sequence of flights an airline schedules for the same aircraft during the day. If an earlier flight arrives late, that aircraft may also be late for its next flight, creating a knock-on delay for passengers waiting to board.
Example: An aircraft is scheduled to fly Berlin to Paris, then Paris to London. If the Berlin-Paris flight arrives 40 minutes late, the aircraft may also leave Paris late for London, even if there is no problem with the London flight itself.
An ATC restriction means air traffic control has limited when, where or how aircraft can operate to keep traffic moving safely. This can happen because of heavy traffic, bad weather, limited airspace capacity or an issue affecting the air traffic control system. Your aircraft can be ready to leave and still have to wait.
Example: If thunderstorms reduce the number of aircraft an airport can safely handle, ATC may hold some flights on the ground or give them later departure times. Your delay in this case may have nothing to do with your aircraft or crew.
A slot delay happens when air traffic management gives a flight a later departure time because the airport or airspace cannot safely handle all the traffic at once. The aircraft may be ready, but it has to wait for its assigned time to leave.
Example: Your flight is ready for pushbacks, but heavy traffic around the destination means ATC has assigned it a later departure slot. You may board on time and still spend another 30 minutes waiting before the aircraft can leave.
The aircraft scheduled to operate your flight is still arriving from its previous flight, so your flight cannot start on time. You may be sitting at the gate while the aircraft is still somewhere else. If that late arrival, then delays your departure, you may also see the term reactionary or knock-on delay. EUROCONTROL identifies late incoming aircraft as a major source of reactionary delays.
Example: A plane flying from Frankfurt to Paris arrives 45 minutes late. It is then scheduled to fly from Paris to Amsterdam. Even if everything is ready for the Amsterdam flight, passengers may have to wait for the aircraft to arrive before their flight can depart.
“Operational reasons” is a broad term airline uses when a delay involves the airline's day-to-day operations. It could refer to crew scheduling, ground handling, late aircraft or other operational issues. The phrase alone does not explain exactly what happened or whether flight compensation may be due.
Example: Your flight from Madrid to Paris is delayed because the aircraft arriving from an earlier European route is late and the crew's schedule has to be adjusted. The airline may simply list the reason as “operational reasons,” even though the actual cause is more specific.
A technical issue means something on the aircraft needs to be checked, repaired or cleared before the flight can safely depart. It could be a relatively minor fault or a problem with an aircraft system. Under EU passenger rights rules, ordinary technical problems linked to normal aircraft operation are generally not considered extraordinary circumstances.
Example:A flight from Barcelona to Rome is delayed after engineers find a fault during a pre-flight check. The aircraft needs to be inspected before it can leave. Even though the issue may be fixed on the ground, the resulting delay can still be relevant when assessing compensation.
A ground stop is an air traffic control measure that temporarily prevents certain flights from departing because the destination or route cannot safely handle more traffic. The aircraft may remain at the gate or on the ground until the restriction is lifted.
Example: A flight from Frankfurt to Paris is ready to leave, but severe weather has reduced the number of aircraft that can safely arrive in Paris. ATC may place the Frankfurt flight under a ground stop, so passengers wait on the ground even though there is no problem with their aircraft.
A diversion happens when an aircraft lands at an airport other than the destination originally planned for the flight. Weather, a technical problem, a medical emergency or another unexpected situation can all lead to diversion. What happens next depends on why the aircraft diverted and how the airline gets passengers to their final destination.
Example:Your flight from Frankfurt to Munich is ready to leave, but overnight frost has built up on the aircraft. The plane needs to be de-iced before departure, and a queue for the de-icing area adds another 30 minutes to your wait.
Minimum Connection Time (MCT) is the shortest scheduled time an airport considers necessary for a passenger to transfer between two connecting flights, including the relevant terminal, security or border procedures. It varies by airport and type of connection.
Example: You have 70 minutes to connect at Frankfurt from a flight arriving from Madrid to one departing for Rome. If your first flight is delayed by 30 minutes, you may no longer have enough time to make the connection within the airport's MCT.
A ground handling delay happens when one of the services needed to prepare an aircraft for departure takes longer than expected. This can involve baggage loading, boarding, refueling, catering, cabin cleaning, or other work carried out while the aircraft is on the ground. The aircraft itself may be ready to fly, but the departure still has to wait.
Example: Your flight from Amsterdam to Paris is ready for boarding, but the baggage team is still loading luggage onto the aircraft. Until that work is finished and the aircraft is cleared up for departure, the flight cannot leave as scheduled.
“Extraordinary circumstances” has a specific meaning under EU passenger rights rules. It generally refers to events outside the airline’s normal operations and control, such as certain traffic control restrictions, severe weather or security risks. When an extraordinary circumstance causes a delay, flight compensation may not be payable. However, passengers may still have rights to care, reimbursement or rerouting, depending on the situation.
Example: Your flight from Paris to Rome is delayed because severe weather has temporarily restricted flights at the destination airport. If the delay was caused by that weather disruption, the airline may not owe financial compensation, although other passenger rights may still apply.
A reactionary or knock-on delay happens when an earlier disruption affects a later flight. The aircraft may arrive late, a crew member may still be operating another service, or connecting passengers may not arrive in time. The term describes how the delay spreads through the schedule, rather than what caused the original disruption.
Example: A flight from London to Paris is delayed by bad weather and arrives 45 minutes late. The same aircraft is then scheduled to fly from Paris to Amsterdam. Because it is arriving late, the Amsterdam flight also leaves behind schedule, even though nothing went wrong with that flight itself.
An airline's delay notification may tell you what happened operationally, but it does not always tell you whether you may be entitled to flight delay compensation. Terms such as “operational reasons,” “late incoming aircraft” or “reactionary delay” can describe a chain of events without explaining the original cause or how it affects your passenger rights.
That is why it helps to look beyond the wording. Airlines may use broad or technical terms when explaining a disruption, and passengers should not have to work out the meaning of aviation terminology before knowing whether they can make a claim.
This is where Click2Refund can help. Instead of asking you to figure out the airline's explanation yourself, Click2Refund checks the details of your disrupted flight and assesses whether you may have a valid compensation claim. If you are eligible, its legal team handles the claim and communication with the airline, making the process simpler from start to finish.
Airlines use terms such as “late incoming aircraft,” “ATC restriction,” “operational reasons” and “reactionary delay” to describe different parts of a disruption. Understanding the term can help you identify what happened, but the wording alone does not determine whether you can claim flight compensation.
necessarily. An airline's label describes the reported reason for the disruption, but compensation depends on the underlying cause, the circumstances and the passenger-rights rules that apply to your flight. A broad term such as “operational reasons” does not automatically rule out a claim.
Possibly. A reactionary or knock-on delay happens when an earlier disruption affects a later flight. The important point is why the original delay happened. The fact that your flight was delayed by an earlier flight does not, by itself, determine whether compensation is payable.