The plane carrying Mrs Merkel's team turned back while flying over the Netherlands late on Thursday, because of a communications failure. The Airbus made a safe but unscheduled landing in Cologne. Mrs Merkel flew to Madrid on Friday then boarded a scheduled Iberia airlines flight to Buenos Aires. Among her fellow passengers on board the Iberia flight was Agustín Agüero, who tweeted a picture of the chancellor on board.
I'm assuming she realized last minute the need to burn her 90k Iberia Avios before Dec 1 and that the MAD - EZE flight was her best bet
Link to twitter picture:
Link to article:
https://www.bbc.com/news/world-europe-46394989