MOSCOW — A Russian man who in 2004 fatally stabbed an air traffic controller he blamed for the death of his wife and two children in a midair collision was briefly detained Saturday in Munich as he traveled to a ceremony observing the 10-year anniversary of the accident in Germany.

The man’s detention, which Russian consular officials protested, once again raised delicate questions of grief and vengeance in the unusual case.

The man, Vitaly Kaloyev, a native of the North Caucasus region of Russia, where blood feuds are still an accepted and parallel system to settle scores, was convicted of murder in Switzerland in 2005, but released two years into an eight-year sentence and deported to Russia.

He was returning to Germany on a flight to Munich to attend the ceremony commemorating the victims of the 2002 midair collision over Lake Constance in southern Germany that killed his family. The police detained him for most of the day on Saturday.