How do standbys and understudies work in opera?

I was just reading a story about an Italian tenor who was a standby at the Met making his debut after the tenor fell ill during a performance of Otello. That makes me wonder how standbys and understudies work in opera. Is this performer hired, flown in from Europe, put up in a hotel, etc. all just in case the lead tenor had a problem? I would have guessed that they would normally have someone more local for that purpose. Do all operas have standbys?

Yes, in international opera houses every role, no matter how small, has an understudy. For the major roles, the understudies (a.k.a. "covers") for the major roles are generally there for the entire rehearsal period and then remain for the entire run of performances. At Lyric they get a good deal of rehearsal, which pays dividends, of course, should they have to go on. Our covers are based all over the country, and a number of them do indeed come to us from Europe. At Lyric there's always a cover run-through near the end of the rehearsal period, so they can be heard in the whole role. In any international house, the cover in a major role is frequently a highly experienced artist who has been notably successful in major roles elsewhere. When the company has a young-artist program, those artists generally cover small, medium-sized, and sometimes quite large roles. The opportunity for a member of a young-artist program to go on in a big role has in some cases turned out to be a true star-making moment for that artist.

To learn more about standbys and understudies at Lyric read Hey! You're on! Lyric's last-minute cast changes.