The intervention increases pressure on US regulators in a dispute between airlines and mobile operators over the introduction of the high-speed mobile broadband technology in the US.
Leading telecom operators Verizon and AT&T were due to start using 3.7-3.8 GHz frequency bands on 5 December, after obtaining licences worth billions of dollars in February.
The Federal Aviation Administration requested further information about the instruments, which can use the same frequency bands as 5G.
The FAA also produced directives limiting the use of radio altimeters in certain situations, sparking US airline fears over the potential costs.
In November, Verizon and AT&T wrote to the Federal Communications Commission confirming their intention to start deploying 5G in January 2022.
But they said they would take extra precautionary measures beyond what is required by US law until July 2022 while the FAA completed its investigation.
The conflict between 5G networks and aircraft equipment led French authorities to recommend switching off mobile phones with 5G on planes in February.
