It has been a tough 13 months for Renault-Nissan CEO Carlos Ghosn. Since August 2013 he has had three highly skilled leaders leave the alliance. Nissan Chief Planning Officer Andy Palmer is the latest 50-something executive to depart.

Palmer, 51, who will become CEO of Aston Martin, follows Johan de Nysschen and Carlos Tavares out the door.

De Nysschen, 54, quit his post as Infiniti CEO in July to become head of General Motors premium brand Cadillac.

Tavares, 56, left his job as Renault chief operating officer last August. His departure came after he said in an interview that he wanted to be a CEO and he saw no chance of rising past Ghosn, 60, who appears to have a lock on the top jobs at Renault and Nissan for as long as he wants them.

Palmer was considered a leading candidate to replace Ghosn as Nissan CEO. He ranked as Nissan’s No. 3 executive behind Ghosn and 60-year-old Hiroto Saikawa, who oversees Asia, r&d, purchasing and manufacturing.

Palmer’s chances to become Nissan’s top boss took a blow when Ghosn said late last year that he wants a Japanese national to succeed him as CEO when the time comes.

Perhaps Palmer was foreshadowing when he stated that there were plenty of choices for the next CEO at Nissan. When asked about his own chances to become No. 1 he said: “At some point, there’s no room on the ladder.”

When that happens, executives with Palmer’s credentials usually find another ladder.