The Federal Aviation Administration (FAA) has banned the 15-inch MacBook Pros that Apple recalled in June, because the lithium battery may overheat and ignite inside an aircraft.
The June recall affected MacBook Pro units sold between September 2015 and February 2017, but Apple also urged customers to check the serial number of the devices on its recall page to confirm whether their battery needs replacing.
The FAA said it alerted US airlines in July to the battery recall affecting some Apple MacBook Pro laptops, ZDNet's sister site CNET reports.
It also reminded airlines of rules issued in 2016 that prohibit them from transporting any products recalled over safety issues in either the cabin or as cargo until the products have been repaired or replaced.
The FAA's Packsafe page for portable electronic devices containing lithium batteries subject to product safety recalls explains the rules fairly clearly.
"RECALLED BATTERIES AND DEVICES: Lithium batteries recalled by the manufacturer/vendor must not be carried aboard aircraft or packed in baggage," the FAA states.
"Battery-powered devices recalled because of lithium battery safety concerns also should not be carried aboard aircraft or packed in baggage unless the device or its battery has been replaced, repaired or otherwise made safe per manufacturer/vendor instructions. The FAA and your airline may offer further public guidance on individual recalled products."
According to the US Consumer Product Safety Commission's page for the MacBook Pro recall, Apple sold about 432,000 of the affected laptops in the US and 26,000 in Canada.
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Apple had received 26 reports of MacBook Pros battery overheating, including five reports of users receiving minor burns, one report of smoke inhalation, and 17 reports minor damage to nearby personal property.
While that's a small number of reports, the potential consequences on a plane could be huge. The FAA's 2016 alert to carriers warned of the risk of the "potential risk of catastrophic hull loss" due to transporting lithium batteries if they caught fire and exploded.
It noted that FAA testing in 2015 "showed that the ignition of the unburned flammable gases associated with a lithium battery fire could lead to a catastrophic explosion", which the current fire suppression system used in Class C cargo was "incapable of preventing".
The FAA was also concerned by testing that showed a single lithium battery in "thermal runaway" will spread to neighboring batteries in the same package and to adjacent packages. Thermal runaway can be caused by battery damage or an adjacent fire.
On top of this, once a battery has exploded, the ignition of a mixture of gases could ultimately spread fire and gases from the cargo compartment to occupied areas of the plane. It notes that only a "few packages" would be enough to create this condition.