NEW YORK — The Metropolitan Opera will consider selling naming rights to its building at Lincoln Center and plans to approach its unions about instituting Sunday performances.

Met general manager Peter Gelb said Wednesday the company also hopes to increase the size of its cramped lobby, which was reduced for financial reasons ahead of the building’s opening in 1966.

“We have to look at all potential opportunities, and certainly the naming of the Met is one of them,” he said.

The Met has named parts of its building after large donors, such as the Sybil Harrington Auditorium and Mercedes Bass Grand Tier, but has not attached a name to its overall building,

Across Lincoln Center Plaza, Avery Fisher Hall was renamed David Geffen Hall this month in exchange for a $100 million donation, and the New York State Theater became the David Koch Theater as part of a 2008 agreement that included a $100 million pledge over 10 years.

Gelb, whose 10th season as general manager starts Monday, said the Met had raised just over $100 million of the $600 million it hopes for in a capital campaign, with half the money intended to increase its endowment, currently worth $266 million. He intends to use some of the money for a one-story glass expansion of the lobby.

“People are crushing the box office an hour before the performance, and the space is inadequate,” he said.

The Met’s schedule calls for evening performances Monday through Saturday each week, with Saturday matinees. Union contracts don’t allow for regular Sunday performances of operas, although there are occasional concerts.

“The need is clear, and I think it’s something that is inevitable,” Gelb said. “It has to happen at some point.”

The Met sold 69 percent of its potential box office capacity last season, down from 73 percent the previous season and 79 percent in 2011-12. But last season’s percentage for Saturday matinees was 85 percent and Saturday evenings nearly 74 percent.

Gelb said he had not discussed Sunday performances with its unions, whose contracts mostly run through 2017-18 and whose agreement would be needed. He said if Sunday shows are added, the Met likely would pick a weeknight to be dark.

“Maybe a Sunday opera would be good for audience development, but I can’t imagine that people are willing to work on Sundays without reasonable compensation and compensatory time off for working the entire weekend,” said Alan Gordon, executive director of the American Guild of Musical Artists.

Following reductions contained in union agreements reached last year, the Met said it finished 2014-15 with a $1 million surplus on $311 million in revenue, up from a $22 million deficit in 2013-14.

Gelb also is working on plans for a MET2GO truck of pared-down, free outdoor productions that would be performed throughout the New York area in June starting in 2016 and 2017. The first production would be Verdi’s “La Traviata” by Dutch director Lotte de Beer, whose staging of Osvaldo Golijov’s “Iphigenia in Aulis” will come to the Met in autumn 2018, after the opera’s premiere in Amsterdam.

RONALD BLUM, Associated Press