The AMC 25 and Regal Cinemas on 42nd Street in Times Square in New York.

Shares of AMC Entertainment skyrocketed more than 10% Monday, thanks to strong demand for "Avengers: Endgame" tickets and renewed confidence behind the company's subscription program.

B. Riley FBR upgraded AMC's rating to buy from neutral on Monday after a positive meeting with management at CinemaCon in Las Vegas last week. The investment firm had previously downgraded AMC in January due to concerns about how well its subscription program "Stubs A-List" would resonate with consumers.

"We believe the impressive advance ticket sales for 'Avengers: Endgame' signals the start of the spring/summer period and we are increasingly optimistic around the potential contribution of Stubs A-List with our updated analysis after meeting with management at CinemaCon last week," Eric Wold, analyst at B. Riley, wrote in the research note.

Wold noted that the Stubs A-List program, which allows moviegoers to see up to three flicks per week, is the likely successor to MoviePass' failed attempt at a similar program last year.

"Knowing the significant traction that was originally achieved with MoviePass before the parent company's financial issues and terms of service changes, we saw an opportunity for one of the major exhibition chains to step in and offer movie-goers a substitute plan," Wold said.

"And with Regal not yet introducing a subscription program following its acquisition by Cineworld over a year ago, our channel checks have indicated a share shift within shared AMC and Regal film markets — which we would expect to continue until at least another plan is introduced," he said.

Additionally, AMC's loyalty program, called Stubs, recently surpassed 19 million members, up from 12 million in the past year.

Stubs A-List costs about $24 per month — about the same price as two adult movie tickets in New York — and requires a three-month minimum at sign-up. There are no blackout dates and subscribers can see films in any format, including IMAX and Dolby Cinema.

In addition, Wold said AMC, which has a market value of $1.7 billion, will reap the benefit of this year's summer blockbusters.

Last week, "Avengers: Endgame" crushed Fandango's first-day U.S. sales record within the first six hours of presales. And on Atom Tickets, the film has sold three times more tickets in the first hour of sales than "Infinity War" did last year. It set a record on the site for the best first hour of presales.

"AMC announced that advance ticket sales have already surpassed the combined first day sales from 'Avengers: Infinity War', 'Captain Marvel,' 'Black Panther' and 'Star Wars: The Last Jedi,'" he said.

Also coming to theaters this summer is "Toy Story 4," "The Lion King," "Godzilla: King of Monsters," "Aladdin," "Spider-Man: Far From Home," "Detective Pikachu" and "Hobbs and Shaw," among others.

Disclosure: Comcast is the parent company of NBCUniversal and CNBC. Fandango is owned by Comcast. NBCUniversal is the distributor of "Hobbs and Shaw."