French Civil Aviation Authority said on Tuesday that the latest generation of 5G smartphones can interfere with aircraft altitude instruments and recommended they should be turned off during flight, reported AFP.

It said, “The utilisation of 5G devices onboard aircraft could lead to risks of interference that could potentially result in errors in altitude readings.”

According to the agency, the potential phenomenon is due to “signal interference from a close frequency source of a strength that is similar or even superior to that of altimeters.”

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The agency added that this interference can cause errors “in instruments that are extremely critical during landing.”

Last week, the agency sent a bulletin on the issue to airlines and recommended that 5G phones should either be turned off completely or put in “airplane mode” during flight.

Since there are concerns that previous generations of mobile telecommunications networks can interfere with a plane’s navigation and communication equipment, most countries have long required that mobile phones be turned off or placed in airplane mode.

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The agency further recommended that in cases of disruption to an aircraft’s equipment that the flight crew immediately notify air traffic controllers who can then alert authorities at the airport.

DGAC also noted that it had laid out conditions for the positioning of 5G base stations in order to limit the risks of interference during landing at French airports.