Airlines and manufacturers say they need more time to retrofit planes to prevent the cell technology from interfering with altimeters.
Wireless companies want to convert the frequencies 3G uses to faster 5G service.
The airlines have warned that a 5G rollout would cause hundreds of flights to be canceled, diverted or delayed.
In November, a warning from the Federal Aviation Administration about safety concerns led to AT&T and Verizon postponing the launch.