Flagstad’s debut at the Met, as Sieglinde in Wagner’s Die Walküre on the afternoon of February 2, 1935 created a sensation, though it was not planned as a special event. Flagstad was virtually unknown in the United States at the time, and the Saturday afternoon slot was usually reserved for lesser-known singers while the top stars performed in the evening. The performance was, however, broadcast nationwide on the Met’s weekly syndicated radio program, and the first inkling of the deluge of critical praise to come was given when intermission host and former Met star Geraldine Farrar discarded her prepared notes, overwhelmed by what she had just heard, and breathlessly announced that a new star had just been born. Days later, Flagstad sang Isolde, and later that month, she performed Brünnhilde in Die Walküre and Götterdämmerung for the first time. Before the end of the season, Flagstad sang Elsa in Lohengrin, Elisabeth in Tannhäuser, and her first Kundry in Parsifal. Almost overnight, she had established herself as the pre-eminent Wagnerian soprano of the era. According to most critics, she still remains the supreme Wagnerian dramatic soprano on disc by virtue of her unique voice. It has been said that she saved the Metropolitan Opera from looming bankruptcy. Her performances, sometimes 3 or 4 a week in her early days at the Met, were quicky sold out at the box office as soon as they went on sale. Though her services in this regard to the Met were not just from box office receipts, her nationwide personal appeals to radio listeners during Saturday matinee intermissions, brought thousands of dollars in donations to the Mets coffers. Fidelio (1936 and later) was her only non-Wagnerian role at the Met before the war. In 1936, she performed all three Brünnhildes in the San Francisco Opera’s Ring cycle. In 1937, she first appeared at the Chicago City Opera Company.
In 1936 and 1937, Flagstad performed the roles of Isolde, Brünnhilde, and Senta at the Royal Opera House, Covent Garden, under Sir Thomas Beecham, Fritz Reiner and Wilhelm Furtwängler, arousing as much enthusiasm there as she had in New York. She toured Australia in 1938, and Hollywood was also interested and tried to cash in on Flagstad fever with her sudden popularity in the US in the mid 1930’s from her many appearances on NBC Radio, The Kraft Music Hall with Bing Crosby, and regular appearances on CBS’s The Ford Sunday Evening Hour. Though Flagstad was not interested in stardom or Hollywood contracts per se, she did make trips to Hollywood during the late 1930’s for pubilicty photo shoots, public appearances, concerts at the Hollywood bowl, and she filmed a rendition of Brünnhilde’s Battle Cry from Wagner’s Die Walküre for the Hollywood variety show anthology The Big Broadcast of 1938 in which she was introduced to american film audiences by Bob Hope. Flagstad is one of two Norwegians, with Sonia Henie being the other, to have her own star on Hollywoods walk of fame.