Avengers: Endgame tickets on sale, US cinema websites crash

With three weeks until Marvel's Avengers: Endgame opens, tickets have gone on sale and promptly caused chaos for US cinema websites.

One final trailer has also been released to showcase Iron Man and Captain America facing off against Thanos.

The websites of AMC Theatres and Fandango couldn't handle the traffic when tickets went on sale this week, which only increases expectations the film will achieve the biggest opening box office opening of all time.

Avengers: Endgame tickets went on sale in New Zealand at 2am on Thursday morning, but at the time of publishing every Hoyts and Event session Newshub checked still had seats available and their websites had no trouble loading.

American fans didn't have it so easy.

"We want everyone to be able to grab their Avengers: Endgame tickets, but it looks like we've gotten Thanos' snap," AMC Theatres tweeted shortly after tickets went on sale.

Around five hours later, they tweeted that the website was back up - but the mobile app was still not functioning properly.

Marvel fans should probably use the toilet before they eventually sit in a cinema for the movie - the Avengers: Endgame runtime is a huge three hours and two minutes.

That makes it almost half an hour longer than Avengers: Infinity War.

Avengers: Endgame's New Zealand release date is April 23.