First-week, advance ticket sales for the newest installment of Marvel's "Avengers" film series have surpassed that of the prior movie by fivefold, Fandango announced Wednesday.

Demand for tickets to "Avengers: Endgame," which opens April 26, has been so high that thousands of showtimes at theaters have been sold out, leading to newly scheduled showings, some at the odd hours of 4 a.m. and 6:30 a.m., Fandango said.

"I wouldn't be surprised to see a record amount of fans reporting sick to work or taking the day off on Friday, April 26 because they'll be attending opening day screenings of 'Avengers: Endgame,'" Variety reported Fandango Managing Editor Erik Davis as saying.

During the first week of #AvengersEndgame ticket sales, we’ve sold 5x the number of tickets sold for Infinity War 💪 pic.twitter.com/uaaP0EKkYb — Fandango (@Fandango) April 10, 2019

Ticket seller Atom Tickets reported Wednesday that on its platform, "Avengers: Endgame" sold almost twice as many tickets as four previous megahits combined: “Aquaman,” “Star Wars: The Last Jedi,” “Avengers: Infinity War” and “Captain Marvel."

Some enterprising fans who have already scored tickets have posted them on eBay, hoping to make profits of hundreds or thousands of dollars. One ambitious seller has listed four seats to an April 28 showing at a New York theater for $20,000.

Robert Downey Jr. in "Avengers: Endgame." Marvel Studio

The hype over "Avengers: Endgame," the 22nd film in the Marvel Cinematic Universe, spiked in December with the release of the trailer. Marvel Entertainment said at the time that it broke the record for the most-viewed trailer in 24 hours, with 289 million hits.

When tickets for the movie first went on sale last week, both AMC Theatres and Alamo Drafthouse reported that for hours their websites were unable to process the overwhelming volume of ticket purchases.

We want everyone to be able to grab their Avengers: Endgame tickets, but it looks like we've gotten Thanos' snap. We're working on getting things back up and running, and in the meantime, please keep trying our website and our partner sites! — AMC Guest Services (@AMCHelps) April 2, 2019

The movie, the direct sequel to "Avengers: Infinity War," stars Robert Downey Jr., Chris Evans, Mark Ruffalo, Chris Hemsworth, Scarlett Johansson, Jeremy Renner, Don Cheadle, Paul Rudd, Brie Larson, Karen Gillan, Danai Gurira, Bradley Cooper and Josh Brolin.