The U.S. Federal Aviation Administration and Boeing have privately issued notifications that the fuel switch locks on Boeing planes are safe.

Fuel switches of the Boeing 787 Dreamliner have come under scrutiny after a preliminary crash report raised questions about how the controls were moved from the "run" to "cutoff" position, starving the engines of fuel.

The notice dated May 15 asked airlines to check if the fuel shutoff valve required replacement. The notice mentioned that the FAA's Airworthiness Directive (AD) addresses a potential unsafe condition affecting fuel shutoff valves installed on the five Boeing planes.