IMDb reports that most of the film’s locations were in Austria. The film’s opening title, which features beautiful snow-capped mountains, was shot in Saalfelden, Austria. Schloss Adler, the mountain fortress where the soldiers raided, was filmed at Hohenwerfen Castle in Werfen, Austria. According to Republic World, the stunning site is free and open to the public and now serves as a museum and falconry center. Werfen was also the location for the train station and the high pastures in the film. The location has been used in other films, most notably the hit classic musical “The Sound of Music” (per IMDb). In “Eagles,” the scenes involving the cable car that took them to the castle were filmed at the Feuerkogelbahn in Ebensee, Austria. All scenes in which both the cable car and the castle appear together were shot using a scale model.
Other Austrian locations for the film are Lofer and Aigen im Ennstal, where most of the village and airfield scenes were filmed. According to Otakukart, filming in Austria took place from late winter to early spring 1968. Varying inclement weather and Richard Burton’s binge drinking led to numerous delays in filming.