At approx 10mins into the film, Lena is looking at the photographs.
She has a glass in her hand, next shot the glass is gone, and the next shot it is back again.
The German ambassador's Mercedes that takes the protagonists to the airport, is flying two German flags. In reality only one would be affixed to the car (on the side where the Ambassador or Charge d'Affaires is seated, behind the driver, not on the driver's side).
At the airport scene, near the movie's end, the sign over the main gate read "Santiago International Airport", which was never the airport's official name. Its official name at that time was "Pudahuel International Airport" (because of its location in that municipality) instead. Besides, the biggest sign should have been in Spanish, and only then in English.
The pilot of the Lufthansa plane is starting the procedure for departure, while the door is still open. This was a common practice until after the September 11, 2001 terrorist attack on the U.S.
When Lena and Daniel are driven to the airport near the end of the movie several large buildings show multiple Satelite-Dishes on their roofs - private sat-receivers were not in use in the seventies.
After the meeting with the German ambassador Lena calls the Ritz hotel to contact the pilot of the Lufthansa crew she was member. But on the seventies there was no Ritz hotel in Santiago. The first one was opened in Las Condes neighborhood, far away from downtown in 2002.
The helicopter landing in the stadium is a MBB BO 105. The military coup took place in 1973, the first BO 105 operating in Chile was built in 1974 (# S-191).