"We got about a minute and forty before the end of the world!"―Lone Starr to Vespa, Dot Matrix and Barf after pressing the self destruct button.[src]
The self-destruct button was the button located on the Spaceball I/Mega Maid that possessed the ability to destroy the entire ship.
The out of order cancellation button
After Spaceball I transformed into Mega Maid, Lone Starr and Dark Helmet engaged in a climatic duel. As the duel went on, Dark Helmet accidentally pressed the self-destruct button due to recoiling from being hit in the crotch by his redirected Schwartz beam as a result of Lone Starr channelling the Schwartz within him, setting a countdown of a little under three minutes. A little before the ship's destruction, the announcement system revealed that there was a cancellation button located on the ship. However, once found, it was found to be out of order. Lone Starr took the time to flee the ship at the last second, while the ship crew evacuated via the escape pods with the exception of Dark Helmet, President Skroob and Colonel Sandurz, who were left behind.[1]