LOS ANGELES (CBSLA.com) — American Airlines recently sent a plane from LAX to Honolulu that was not cleared to make the long voyage over the ocean.

On Aug. 31, the airline sent a twin-engine A321 on the five-and-a-half hour flight across the Pacific Ocean, despite the fact that the plane lacked safety equipment required by federal authorities for all planes making long flights over water. Those items included oxygen tanks and a special fire-suppression system.

The violation was an unusual transgression, said aviation expert and reporter Brian Sumers, who first reported the incident on his blog.

“Airlines just don’t make these sorts of mistakes,” Sumers said.

With the correct safety equipment, flights are certified to fly for as long as three hours with just one engine in order to reach an alternate airport in the case of an emergency. Without that equipment, flights are restricted to making long flights over land. The carrier has both categories of planes but sent the wrong one in this case.

An American Airlines employee in Dallas realized mid-flight that the airline had sent the wrong plane but elected to continue the flight. The return flight was canceled and the plane was sent back to the mainland without passengers.

The airline said it has reviewed the incident and is taking steps to prevent a repeat of the incident in the future. The company only started flying the A-321 to Hawaii last month.

“When we noticed it, we immediately undertook an internal investigation, and we alerted the FAA,” an American Airlines spokesman said. “We are checking our internal procedures, everything that led up to the departure. We are going to figure out what we can do better. We have gone back and made some changes to software systems.”