A four-star general and 27 other military officers appeared in court in Turkey on Monday charged with plotting to undermine the government.
General Bilgin Balanli was in line to become commander of the air force until his arrest three months ago.
He is among hundreds of officers accused of planning to bring down the governing AK Party led by Recep Tayyip Erdogan in 2003.
The BBC reports 200 officers went on trial last December on similar charges.
The chief of the armed forces resigned last month, along with the heads of the army, navy and air force.
General Balanli and his co-defendants are accused of taking part in a plot codenamed Sledgehammer that reportedly involved plans to bomb mosques and provoke tensions with Greece, in order to spark political chaos and justify a military takeover.
The BBC reports details were presented to a seminar in 2003, a year after the AK Party came to power.
However, the defendants argue that the plan was a theoretical scenario to help them plan for potential political unrest.
Turkey had three military coups between 1960 and 1980.
