Union members at the airline and its subsidiary LTU gave Cockpit the power to declare a strike as early as this week following months of inconclusive haggling over contracts, Cockpit said.
If there are no further improvements within the coming days, “labour dispute means will be unavoidable in August,” they added.
The vote among the pilots was almost unanimous, with 99 percent at Air Berlin and 97 percent at LTU approving Cockpit's right to call a strike to end the disagreement.
Pilot complaints include daily changes to schedules and the failure to provide a third pilot on long-haul flights – a practice that is standard for other airlines, according to Cockpit.
“We have gotten closer on many points,” Air Berlin spokesman Christoph Noack said, adding that further options remain.
Further negotiations are scheduled for Tuesday, Wednesday and the second week of September.
In March Cockpit called off a planned strike because Air Berlin had improved its offer, but the two sides have failed to make an agreement since then.