Embarrassed by a concessions-stands failure and angry customers on Opening Night Friday at Safeco Field, the Mariners announced Tuesday they will offer free tickets for home games in April or May, as well as a credit at the stands.

The make-good is for fans who experienced long lines during the game due to a failure of the software system that operates cash registers and processes credit cards.

Some fans reported waiting for more than an hour and missed three innings or more. The registers began failing shortly after the gates opened, and by mid-game more than 200 of the 400 point-of-sale stands were a cash-only operation. Software engineers determined that the only solution was a shutdown and re-boot, which resolved the problem by the eighth inning.

“We always want our fans to have a positive experience,” Mariners president Chuck Armstrong wrote in a statement released before the game Thursday. “What happened Friday night was unacceptable and I offer my sincere apology to all of the fans who suffered through the long lines and inconvenience. The guest experience on Opening Night was nowhere close to meeting our standards and we want to make it up to our fans.”

Here’s how the make-up will work for 18 home games beginning Wednesday through the end of May:

• Locations will be in the same seating level as Opening Night tickets.
• Those seated in Suites, Diamond Club, All-Star Club and Hit It Here Café will get the choice of Club or Main Level tickets.
• Each make-good ticket will come pre-loaded with a $5 TicketPlu$ credit that can be redeemed at concession stands.
• The Mariners have email addresses for most people who purchased tickets for Friday’s game and will receive information by email on how to receive their free tickets.
• Fans can claim their free tickets by showing their ticket stub or proof of purchase at any Mariners Team Store or the Safeco Field box office.
• Anyone who does not have a ticket stub or proof of purchase can call 206-346-4001, the Mariners Customer Service Hotline, between 8:30am-5:30pm for assistance.
• More information about the offer is available at www.mariners.com/OpeningNight.

Staff from the software provider, Micros, have been doing a thorough review of the system since. No problems were reported Saturday or Sunday.

“We promise our fans that we will get to the bottom of what caused the failure so that it doesn’t happen again,” Armstrong wrote. “We hope our fans will give us a second chance to provide a great experience at Safeco Field.”