Guest appearances with the Montreal and Los Angeles symphonies both led to permanent positions; in 1960 he became music director in Montreal and associate conductor in Los Angeles. Thus Mehta became one of the first of a new breed of conductors sometimes called the "jet set," who are able to maintain two (or even more) principal conductorships of major orchestras by means of frequently flying between the cities involved.
Mehta's accomplishments in Los Angeles, where he became musical director in 1962, were particularly striking. In just a few years he was able to turn the lackluster ensemble into one of the nation's finest orchestras, and, still under 30 years of age when he was appointed, he became the youngest music director of any "major" U.S. orchestra. An exuberant, extroverted performer and person, he possessed a genuine star quality; soon, he conducted the orchestra on a notable series of excellent recordings for London (Decca) Records. Mehta made his operatic debut at the Metropolitan Opera in New York on December 29, 1965, and in 1967 he resigned his position in Montreal, and forged a new relationship with the Israeli Philharmonic Orchestra, eventually becoming its chief music adviser in 1970. In 1971 he conducted the Los Angeles Philharmonic on the soundtrack of Frank Zappa's film 200 Motels. In 1978 he resigned his Los Angeles post to succeed Pierre Boulez as music director of the New York Philharmonic Orchestra. After the rather ascetic, ultra-modern Boulez, Mehta's interest in lush Romanticism, and a more traditional repertoire made for a favorable impression, and a long and successful relationship with the orchestra. However, by the time of his resignation in 1991, a little of the bloom had faded from his relationship with the critics, some of whom seemed to be put off by the more "Hollywood" aspects of his style and personality.
In 1990 Mehta was asked to conduct the first of the now-legendary Three Tenors concerts. Mehta proved a highly appropriate choice, being one of the few conductors with the charisma to match the well-practiced stagecraft of the three star tenors. The concert was a huge success, with a worldwide television audience, and enormous record sales. When the phenomenon was repeated in 1994 from Los Angeles, Mehta again conducted.
Between 1998 and 2006, Mehta was music director of the Bavarian State Opera in Munich. He made several tours and kept up a busy schedule of guest conducting appearances. He has continued to serve as Music Director for Life of the Israel Philharmonic.