American Airlines confirmed Sunday that they accidentally sent a wrong plane to Hawaii from Los Angeles in late August. The inadvertent flying violated the Federal Aviation Administration (FAA) regulations, which require special certification whenever long-haul flights over the Pacific are made.

According to American Airlines spokesperson Casey Norton, it was after AA Flight 31 had departed the Los Angeles International Airport on Aug. 31 when the mix-up was noticed, CNN reported. The uncertified Airbus A321S was filled with over a hundred passengers and crew. Norton added that company promptly notified the flight crew and the FAA. Eventually, a decision was made, which allowed the crew to complete the flight and the plane safely landed in Honolulu.

"The flight departed and landed safely without incident," Norton told BuzzFeed News. "When we realized what happened, we immediately called the FAA and notified them."

FAA usually requires long-hauled flights over large bodies of water, which have no suitable alternative landing locations, to have a certification called ETOPS (Extended-range Twin-engine Operational Performance Standards), The Sydney Morning Herald noted. It means that the Hawaii-bound aircraft should have extra fire suppression equipment in the cargo and extra medical equipment on board including oxygen, in case an on-board emergency transpires. However, during the mix-up, American Airlines reportedly bypassed the rule.

Meanwhile, American Airlines acknowledged that the Aug. 31 mix-up was definitely a big yet extremely rare mistake. Aviation blogger Brian Sumers, who first reported the incident, was even shocked about the issue.

"It's really rare," Sumers said. "Something like this, when you talk to airline people, they say 'How does this happen? This can't happen.'"

American Airlines, which is a codeshare partner of Qantas, did not reveal the cause of the mix-up. But Norton said the airline immediately upgraded the software on the plane to ensure that "the correct aircraft is identified to fly the correct route."

In other news, two commercial planes collided into each other on Sunday evening on the LAX tarmac. As per CBS News, United Airline Flight 199 came into contact with an Alaska Airlines jet near Terminal 7 after landing from New Jersey. No casualties were reported to about 340 passengers however, their flight schedules were greatly affected.