A plane not certified to travel for long distances over water was used to fly from Los Angeles to Hawaii last month, American Airlines has confirmed.

Passengers arrived safely to their destination after the 31 August incident, in which an A321S plane was used instead of a A321H.

The A321S has less safety and medical equipment on board than the A321H.

American Airlines is investigating the plane mix-up with the Federal Aviation Administration.

“Whether the plane was going to make it there was never a question,” company spokesman Casey Norton told the DailyReleased.

Mr Norton said the two planes are equipped with the same engine, fuel tanks, range and basic safety features.

The A321H plane, because it is used for long flights, comes with more medical supplies and safety features like fire suppression.

“We’re reviewing our procedures and looking at everyone involved,” Mr Norton said.

The airline has revised its software to properly identify the correct aircraft are operating the correct routes, he said.

He said the A321S plane flies over water regularly for many missions but is not extended-range twin-engine operational performance standards (ETOPS)-certified, which the airline requires for flights to Hawaii.

The A321S plane comes with four slide-rafts and a portable raft, along with life jackets and seat cushions that can be used as flotation devices, the same as the A321H, Mr Norton said.