Pilots have stopped 222 deportations of asylum seekers from Germany by refusing to take off with them on board.
Many of the pilots refused to take control of flights taking people back to Afghanistan, where violence is still rife following years of war and occupation by Western forces.
One of the airlines involved said pilots made the decisions on a "case-by-case" basis if they believed "flight safety could be affected".
Germany has deemed Afghanistan a "safe country of origin" in some cases, despite ongoing violence and repression in parts of the country.
Between January and September, a total of 222 planned deportations were classified to have "failed" due to pilot refusal, according to German government figures. Most – 140 – occurred at Frankfurt airport. Others refused to fly from Cologne-Bonn airport.
The figures were obtained by the Die Linke political party, which is commonly referred to as the Left Party.
Some of the flights belonged to Lufthansa and its subsidiary, Eurowings.
The decision not to carry a passenger, was ultimately down to the pilot on a "case-by-case decision", Lufthansa spokesman Michael Lamberty told the Westdeutsche Allegeimeine Zeitung newspaper which originally reported the story.
He added: "If he has the impression that flight safety could be affected, he must refuse the transport of a passenger.
"Should security personnel at the airports have some sort of information in advance which indicates that a situation could escalate during a deportation, they can decide ahead of time not to let the passengers board."
German publication RBB24 quoted a Lufthansa pilot who did not want to be identified as saying pilots would normally refuse to take off if a potential deportee answers "no" when asked if they want to take the flight.
"We have to prevent anyone from being freaked out during the flight, and we have to protect the other passengers as well," the pilot reportedly said.
Pilots can face disciplinary measures if they refuse to fly on moral grounds.
Lufthansa Group spokesman Helmut Tolksdorf told RBB24 that he was not aware of "any case where one of our pilots has refused to take them for reasons of conscience".
Germany processed more asylum applications than all 27 other EU countries combined. European statistics agency Eurostat, said the Federal Office for Migration and Refugees (BAMF) decided 388,201 asylum cases in the first six months of 2017.
At least one similar refusal is known to have taken place in the UK when British Airways pilot refused to take off while Samim Bigzad was on board earlier this year.
Mr Bigzad, an Afghan, faced deportation to the city where the Taliban had threatened to kill him.
“You’re not going to take him; I’m not flying," the pilot said. "Someone’s life is at risk.”
* Update. This article and headline have been corrected to reflect the fact that 222 asylum seekers' deportations from Germany were prevented by pilots refusing to fly, rather than a total of 222 flights being grounded by German pilots. 6/12/17
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