With dozens of strikes at Heathrow Airport on the agenda and further disruption expected from attacks on air traffic controllers, this month’s passengers could also face with nine days possible delay due to “the largest air force deployment exercise in NATO history”.

Air Defender 23, focused on Germany and managed by the Luftwaffe, will involve more than 10,000 military personnel and 250 fighters from 25 countries – with at least 800 civilian aircraft diverted each day .

These are the key questions and answers.

What is happening?

In fact, Nato is placing sugar blocks in the sky. Vast swaths of airspace over Germany and neighboring countries will be closed to civil aircraft during the multinational exercise – which runs from Monday 12 to Thursday 22 June (although it will not Weekends Saturday 17th and Sunday 18th June are closed).

Civilian pilots will need to navigate around three main “clusters” where flying is restricted or prohibited at different altitudes. Each will be closed or severely restricted to civilian traffic for several hours each day.

Why is Nato taking over central Europe right when millions are trying to fly to the sun?

The stated purpose of the exercise is to “optimize and expand cooperation among the participating countries”, with the exercises modeled on “NATO Article 5 support scenario”.

Article 5 means: “If a NATO ally is the victim of an armed attack, each and every other member of the alliance shall treat this act of violence as an armed attack against all members and will take such actions as they deem necessary to assist an ally under attack.”

In other words, the exercise has a training value, but also a strong political dimension: showing the Kremlin what would happen if, for example, Russia attacked one or more Baltic republics.

“The procedures are currently being optimized to minimize the impact on civil air traffic as much as possible,” said the Bundeswehr (German defense force).

But travelers this month must overcome another hurdle on their way to their destination.

What is the end result for those who want to go on vacation?

The exercise comes as European skies are busier than at any time since 2019, before the Covid pandemic – and as European air traffic control agencies are struggling to cope with the surge. post-Covid flight operations, as well as the closure of airspace in other countries. Russia and Ukraine.

Delays and longer flight times “will be inevitable”, according to Deutsche Flugsicherung, German air traffic control service provider. This is due to the expected dynamic nature of this unique large-scale exercise as well as the existing complexity of the system, it said.

“Around 800 flights will be rerouted daily due to the exercise and related measures,” said Eurocontrol, the agency that monitors the skies above Europe.

About 300 flights will have a route extended by an average of 70 miles (110km), which corresponds to about 7 minutes of cruising at cruising speed. While that may sound like a modest impact, the closure will put additional pressure on the airspace that remains open.

With finely adjusted schedules, delays can quickly add up – and cause problems with crew working hours and curfews at some of Europe’s top airports, including London Heathrow.

Which routes are most likely to be affected?

The southern cluster will significantly affect many holiday flights. Departures from London to Antalya in Turkey often fly directly through the area, as do flights from Manchester to the Greek islands.

It will also affect Lufthansa’s main hub, Frankfurt. Further north, flights to Berlin, Poland and Denmark could be affected

In addition to some aircraft flying on longer routes, Eurocontrol has also warned that the average expected flight path delay for each flight due to the exercise is between 150 and 180 seconds. Again, that seems trivial.

But with low-cost airlines like Ryanair, whose flights are only 25 minutes apart between arrival and departure times, air traffic control delays can quickly form and affect schedules.

The German government has asked each state to relax the curfew at the airport during the exercise in case there is a delay.

What is your worst case scenario?

Once flows into and out of key airports – such as London Heathrow and Gatwick – are disrupted, other problems will begin. These are the busiest airports with two and one runway respectively in the world.

If a significant number of aircraft differ from their schedules, it becomes difficult to manage take-offs and landings. Furthermore, late departures may block the arrival gate.

Gatwick’s largest airline, easyJet, is downplaying the possibility of disruption. A spokesperson said: “For now our schedule is expected to operate as normal. We are in close contact with the German authorities and all of our partners and will continue to monitor the situation closely to ensure the impact on operations is minimal.”

Opposite Heathrow, the largest airline – British Airways – is working with relevant authorities to model possible impacts. But until first exposure, no one knew what the impact might be.