TWO major United States airlines have banned shipments of lithium-ion batteries on board their planes, according to a BBC report last week.

In the report on March 3, the BBC reported that United Airlines and Delta Airlines had stopped bulk shipments of the batteries, amid concerns by aviation officials that they had contributed to fires that downed two cargo planes, killing four people.

"Our primary concerns when transporting dangerous goods are the safety of our customers, our customers' shipments and the environment," the BBC quoted a United Airlines statement.

A UPS Airlines cargo plane crashed in Dubai in 2010, killing both crew members, after a fire erupted on board. A probe by the Federal Aviation Administration (FAA) found that it was carrying a large number of lithium-ion batteries.

An Asiana Airlines cargo plane crashed into the sea in 2011, killing both crew members. It was carrying 400kg of lithium batteries.

Malaysia Airlines flight MH370, a passenger flight from Kuala Lumpur heading to Beijing that went missing one year ago, was also reported to have been carrying 221kg lithium-ion batteries in its cargo. They did not go through security screening before being loaded onto the flight, an interim report from an international investigation team revealed on Sunday.

Tests by the FAA had found that fires could ensue if batteries were overheated, according to the BBC.

It put 5,000 lithium-ion batteries next to a heater, which caused the batteries to heat up to about 600 deg C. An explosion and fire ensued.

The same thing happened even after a fire-suppression agent was added.

Lithium-ion batteries are found in electronic devices like cellphones and laptops, and are used as a source of rechargeable power.