Le Vernet - Unidentified remains from the 150 victims of the Germanwings flight that crashed in the French Alps in March were buried quietly overnight ahead of a ceremony for families on Friday."The burial took place overnight in the cemetery at Le Vernet, discreetly," said Bernard Bartolini, mayor of Prads-Haute-Bleone, one of the Alpine communities affected by the crash.Up to 500 people were expected later on Friday for a ceremony in honour of the victims - which included 72 Germans and 50 Spaniards.All 150 people on board died instantly when, according to investigators, co-pilot Andreas Lubitz deliberately crashed the flight into the mountains.The mayor of the town of Le Vernet, where Friday's ceremony was due to take place, said the unidentified remains were buried in a collective grave."For the families of the victims, it's a second burial because they have already buried the remains of their loved ones that could be identified by DNA," Francois Balique told AFP.He said there was "no other solution" than to bury the unidentified remains in a mass grave."It will be terrible for the families," he said.The chief executive of Lufthansa, Carsten Spohr, will not be attending Friday's ceremony amid a spat between the airline - the parent company of Germanwings - and families over compensation.The relatives of the German citizens killed in the March 24 disaster have turned down Lufthansa's compensation offer and accused it of ignoring their suffering.The parents of 16 student victims from the town of Haltern wrote an open letter to Spohr to voice "disappointment" at Lufthansa's conduct "since a pilot from your company killed our children".Lufthansa disbursed €50 000 per victim in immediate aid after the crash.It said on June 30 that it would additionally offer compensation of €25 000 to the families of each of the 72 Germans killed, plus €10 000 to each immediate relative, including parents, children and spouses.But the 32 parents of the Haltern students wrote that to put this value "on the life of each of our children and on our pain" was deeply offensive.They are demanding a "six-figure sum", their lawyer said.A Lufthansa spokesman told AFP that "because of the tense atmosphere created in recent days by the open letter, Carsten Spohr will not be attending the memorial service at Le Vernet.""He does not want to disturb the ceremony with this issue," the spokesman added.The company will be represented by Thomas Winkelmann and Simone Menne, two top Lufthansa officials.