Endgame begins playing in previews on the evening of April 25, a Thursday. Fandango reports that thousands of shows are sold out throughout the weekend, prompting theater chains to add more screenings around the clock (that's not unprecedented for a big Hollywood tentpole).

Those who want to see the superhero pic at Regal L.A. Live at 5:30 a.m. April 26 are out of luck, for example. All seats have been snapped up, according to a Fandango seating chart. And the 2:30 a.m. viewing of Endgame in Imax 2D at AMC Century City in L.A. is almost sold out, while the 5:30 a.m. 3D screening is at capacity.

In New York City, the AMC Empire 25 — the busiest multiplex in the country — will continue to offer screenings of Endgame every 15 minutes or half hour between 1 a.m. and 5:30 a.m., following the usual Thursday evening schedule and before official Friday showtimes commence.

Fandango says some of its theater partners are also adding 6:30 a.m. shows on April 26.

“I wouldn’t be surprised to see a record amount of fans reporting sick to work or taking the day off on Friday because they’ll be attending opening day screenings," Fandango managing editor Erik Davis says.

The tentpole has a shot at scoring the biggest domestic opening in history, beating Infinity War ($257.6 million) and Disney and Lucasfilm's Star Wars: The Force Awakens ($248 million). It's also poised to shatter the global record set by Infinity War ($640.5 million) with a worldwide launch of $800 million or more.

The big question mark — Endgame runs three hours and one minute, the longest of any MCU title and meaning one fewer showtime a day, on average (Infinity War was two hours and 29 minutes). Disney and Marvel will try to compensate by booking as many screens as possible within any given multiplex.