According to reports Gen Tariq Mohammed Abdullah Saleh was sacked on 6 April along with nearly 20 other senior officers as part of a restructuring of the armed forces.
But he refused to accept the decision of President Abdrabbuh Mansour Hadi.
One unconfirmed report said Gen Ahmar had been appointed assistant to the defence minister after agreeing to step down as air force chief.
President Hadi’s decision to replace senior military officers, including Gen Ahmar and Gen Saleh, was agreed by Yemen’s main political parties.
It was also supported by the United States and neighbouring Gulf states, which brokered a power-sharing deal that saw Mr Saleh step down in November.