President Ma Ying-jeou instructed the Ministry of National Defense (MND) Thursday to look into several military plane crashes that have occurred since he took office slightly more than a year ago. 'I'm sad to see the four or five military plane crashes involving all three branches of the armed forces since I assumed the presidency, ' Ma said while presiding over a commissioning ceremony for newly promoted officers. Since Ma assumed the presidency May 20 last year, five military plane crashes have been reported, leaving nine pilots dead and seven others injured. In the latest incident, an air force twin-seat F-5F jet fighter crashed into the sea off the outlying island of Penghu Wednesday, killing both officers aboard. Ma said the Defense Ministry should conduct an in-depth review to find out what caused the tragedies. 'We should get to the bottom of whether they were caused by mechanical failure or pilot error,' Ma added. Noting that pilots take a long time and a lot of money to train, Ma said the loss of every single pilot is a heart-rending tragedy not only for his family but also for the country. He said the military should on the one hand maintain normal operations and make timely replacement of obsolete or worn out military equipment, while on the other should strengthen manpower training to reduce accident rates. Meanwhile, touching on a drive to wipe out corruption in the military, Ma said the ministry should conduct an extensive review of efforts in this regard every three months. Describing honor as being more important than life for military personnel, Ma said the anti-corruption campaign is partly aimed at clarifying speculation among the public. 'We do not suppose that every officer involved in the probe is a criminal. Our goal is to clear the name of suspected officers through strict and impartial investigations,' Ma noted. In handling suspected corruption cases, Ma went on, several principles should be observed, including no perversion of justice, a proper investigation, speedy conclusion and heavy penalties for serious crimes. On military combat readiness, Ma said the military cannot afford to relax manpower training and arsenal renovation because China still deploys more than 1,000 missiles aimed at Taiwan. 'Despite a thaw in the once-strained relations across the Taiwan Strait, our defense policy of maintaining an elite deterrent force remains unchanged,' he added. 