Previously, pilots with the rank of captain were allowed to fly beyond 62 under a re-employment contract renewable each year until the age of 64.
First officers have not been offered re-employment beyond age 62 since January 2013.
The airline said it is trying to reduce a pilot surplus which is expected to continue into the 2015-2016 financial year.
"The situation has not improved due to network changes, the challenging business environment and despite measures already taken to alleviate the surplus," SIA said in a statement sent to AFP.
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"SIA was forced into this cost-cutting measure because of the surplus of pilots it has," said Shukor Yusof, founder of aviation research firm Endau Analytics in Malaysia.
"SIA's revenue is falling amidst stiff competition from budget carriers and a struggling premium segment... And it can no longer afford the same number of pilots it once had," he told AFP.
The airline reported last November that its net profit in the half-year to September plunged 55.5 percent, weighed by heavy losses in budget carrier affiliate Tiger Airways.