AT&T and Verizon have agreed to further delay the rollout of 5G wireless services in the US after additional consultation with regulators over the network’s potential interference with aviation safety, in an about-face one day after the telecoms groups vowed they would forge ahead.

Both companies said they would postpone the debut of their ultrafast wireless networks, scheduled for Wednesday, by an additional two weeks, bowing to a request from the transportation department and the Federal Aviation Administration submitted on December 31.

The move was a stunning reversal by the two telecoms, whose chief executives on Sunday pledged in a joint letter to regulators to continue with the scheduled 5G rollout, with service modifications around airports for six months.