The delay clouded plans for her meeting with President Donald Trump at the summit, though German government spokeswoman Martina Fietz said the chancellor will try to reschedule all of her bilateral talks.
Video from on board shows several fire engines surrounding the Airbus after it landed.
"Why now?", Merkel asked. "Now we have one more minor problem".
The captain announced the plane's electronic systems had failed, rendering it unable to cross the Atlantic.
Kim Open to Allowing Inspectors Into North Korea's Main Nuclear Site
However, North Korea believe that you first need to remove the sanctions and to formalize the end of the Korean war of 1950-1953. North Koreans are usually forbidden to enter Japan , under the sanctions imposed on Pyongyang for its missile and nuclear tests.
Saudi Crown Prince sidelined in G20 family photo
Trump administration officials on Sunday continued to stress that point and emphasised the importance of the United States' maintaining a close relationship with Saudi Arabia .
Despite progress, new HIV diagnoses in Europe ‘alarmingly high’
Injecting drugs and heterosexual intercourse are the most common reasons for the transmission of the disease in this region. Since the start of the AIDS epidemic in the 1980s, more than 77 million people worldwide have become infected with HIV.
In a weird incident involving Merkel's official plane in 2013, a 24-year-old intruder high on drugs and wearing just underpants managed to get aboard the parked jet in Cologne and stage what media termed "a one-man party" before he was arrested.
The aircraft lost communications for almost an hour, forcing it to make an emergency landing in Germany's Cologne-Bonn airport. She is unlikely to arrive until Friday evening and it was not immediately clear which meetings would have to be rescheduled. Leaving shortly after midnight, she told reporters there had been a "serious problem". Embarassingly for the German government, out of a fleet of 128 aircraft officially on the Luftwaffe's books, those four were at the time the only Eurofighters in Germany capable of flying combat missions due to a lack of spare parts. Merkel is expected to meet Russian President Vladimir Putin to discuss Syria and Ukraine, including the recent incident in the Kerch Strait.