U2 singer Bono was travelling on a private plane from Dublin to Germany on Wednesday when the Learjet 60 he was travelling on lost one of its doors.

An official from the German Federal Bureau of Aircraft Accident Investigation told ABC News, “The Learjet lost a door where the luggage was put in,” and continued, “Either something broke on the door or the door wasn’t closed properly. Those are the usual problems that occur.”

The Daily Mail reports that Bono was traveling with four friends when the incident occurred, flying at 8,000ft (2,400m) as they reached the German coast. A source close to the singer told the paper that only when the plane landed did those inside it become aware of what had happened.

“The entire door along with Bono and his companions’ luggage had fallen out mid-air. They don’t know if the door and the contents landed over water or land but they were extremely lucky. They were at an altitude where anything could have happened and they are all feeling very lucky to be alive,” the source said.

Bono and the rest of U2 are due to attend the Bambi Awards in Berlin on Thursday, where they will be presented with the Music International award and perform live. The Bambis are Germany’s oldest media awards, whose statuette “pays homage to the heroes of our time who have touched and inspired us with their actions, talents and visions.”

Bono and his entourage were traveling ahead of the rest of the band, as the singer had a prior engagement with Gerd Mueller, German Minister of Economic Cooperation and Development. On Wednesday the German Foreign Office tweeted a picture of an unscathed Bono with Walter Lindner, the Bundestag’s special representative tasked with the Ebola response, adding that the two exchanged ideas about the fight against the virus.

According to ABC News, Germout Freitag, the German official who briefed the media, said that the investigation into the incident could take up to a year to complete. NBC News reported that Freitag anticipated problems in finding the lost objects: “The aircraft and its rear door are painted black, so the search in the wooded area will be difficult.” Investigators are to search the vicinity of Berlin’s Schoenefeld airport for the missing luggage and door, which will help them determine the cause of the incident.