The most recent Lufthansa strike that started last week has now impacted more than half a million travellers as it continues this week. Here's what you need to know about how it could affect you.
Lufthansa pilots went on strike for four days last week, and have resumed their walkout again this week on Tuesday and Wednesday.
Here's what you should know about the ongoing labour battle.
1. Why are the pilots striking?
Pilot union Cockpit is calling for a pay rise of an average of 3.66 percent per year, retroactive for the past five years. The union says pilots have endured a wage freeze over that time and suffered a "significant loss of purchasing power" due to inflation, while Lufthansa has made billions in profits.
But managers have rejected such a settlement, with their last offer a one-off bonus of just under two months' salary and a 4.4 percent pay increase spread over two years - a deal refused by Cockpit at the weekend.
"The starting point is that we already pay our pilots far better than our competitors," said Lufthansa's hub management board member Harry Hohmeister last week.
2. How long has this dispute been going on?
This is the 15th industrial action called by pilots' union Cockpit since April 2014. Over the past two years, the union and the company have fought over pay increases.
Labour disputes erupted around two years ago when management sought to cut costs, saying the current retirement system was too expensive to maintain in the face of competition from low-cost rivals like Ryanair and Easyjet.
During this time, the company has also been battling with cabin crew staff, who last November staged the longest walkout in Lufthansa's history with a seven-day stoppage, forcing the cancellation of 4,700 flights and grounding 550,000 passengers.
An expert with the Cologne Institute for Economic Research, Hagen Lesch, told the Südkurier
last week that the larger issue at stake for pilots is about the company's future business structure and the influence of budget airlines, like Lufthansa's low-cost Eurowings - which has also faced its own labour disputes
3. How much are pilots paid?
According to DPA, Lufthansa pilots are among the best paid employees in German, and the airline affirms that its pilots are among the top earners in the sector, but there are different estimates for how much they actually make.
AFP, for example, reports that co-pilots at the start of their career earn €6,500 euros ($6,890) gross per month, while a late-career captain earns more than €22,000 euros - that's between €78,000 and €264,000 annually.
For veteran pilots, GehaltsReporter.de estimates that they can earn up to €250,000 or more per year. Handelsblatt estimates pilots with 20 or more years of experience could earn €225,000.
But how do they actually stack up compared to other companies?
This answer is a bit complicated because it varies greatly among airlines - which is part of what Lufthansa pilots are concerned about, given competition from budget airlines.
For example, GehaltsReporter.de reports that Air France KLM pays relatively high, with pilots starting at €134,000 (compared to €106,000 at Lufthansa), but co-pilots start at €49,000.
German Tui Fly pays co-pilots €63,000 to start, according to GehaltsReporter.de, while captains start at €106,000 and can make up to €204,000.
But at Ryanair, co-pilots start with €25,000 and pilots can make up to €85,000 maximum.
4. Who is impacted by the current strike?
As of Tuesday's walkout, the most recent round of strikes has now hit more than half a million passengers as 4,461 flights have been cancelled since last Wednesday.
Both short- and long-haul flights have been impacted.
Lufthansa group's other airlines - Germanwings, Swiss, Austrian Airlines, Air Dolomiti and Brussels Airlines - will not be affected by this week's strike.
5. What happens to travellers whose flights are cancelled?
If your flight was cancelled, the airline is offering customers to re-book or cancel their flights for free. If you are flying within Germany, Lufthansa is also giving out Deutsche Bahn train vouchers in exchange for air travel.
Those whose flights were cancelled may also request a refund.
Those flying during strike days with Lufthansa, Austrian Airlines, Swiss or Brussels Airlines also may transfer their booking without a fee, regardless of whether their flight was cancelled.
Last week the company booked thousands of hotel rooms in the Rhine-Main and Munich areas - the homes to Germany's busiest airports - as a precaution. Lufthansa had also set up folding cots for passengers who could leave the airport due to visa restrictions, and employees were providing affected travellers with beverages, snacks and “telecommunication options”.
6. What will this cost Lufthansa?
Repeated strikes at Lufthansa have caused "long-term" damage to the group's reputation, said Guido Hoymann, an air travel sector analyst at Metzler bank.
"Lufthansa's reliability has been called into question," he said, adding that the group could lose customers - especially from its sizeable business segment.
In purely financial terms, the impact has so far been smaller.
One strike day costs the group between €10-15 million, Lufthansa says.
In 2015, the group lost around €100 million to strikes - a large figure but one that remained dwarfed by its record profit of €1.7 billion.