The International Civil Aviation Organization (ICAO) has prohibited shipments of lithium-ion batteries as cargo on passenger aircraft, responding to concerns by pilots and airplane manufacturers that they pose a fire risk.

A 2015 paper published by an aircraft manufacturing trade group found that existing fire-fighting systems on airliners could not “suppress or extinguish a fire involving significant quantities of lithium batteries.”

The ban, which is mandatory for ICAO member states, will take effect April 1, and will be maintained until a new fire-resistant packaging standard to transport the batteries is designed.

“Safety is always our most fundamental priority,” said Dr. Olumuyiwa Benard Aliu, ICAO Council President. “This interim prohibition will continue to be in force as separate work continues through ICAO on a new lithium battery packaging performance standard, currently expected by 2018.”

The ban applies only to lithium-ion batteries shipped as cargo on passenger aircraft, not to those contained in personal electronic devices carried by passengers or crew. Li-ion batteries can still be transported on cargo planes.