Effective July 24, 2008, the FAA extended the validity period of pilot medical certificates. This change will allow some pilots to visit the aviation medical doctor less often.
The extension applies only to first and third class medical certificates issued to pilots under the age of 40. Under the old rule, a third class medical certificate, required for the operation as a private pilot, issued to a pilot under the age of 40 was valid for 36 calendar months (3 years). The new rule extends that period to 60 calendar months (5 years)
Likewise, the first class medical, required when a pilot exercises his privileges as an Airline Transport Pilot (ATP), will be extended, for pilots under the age of 40 from 6 calendar months to 12 calendar months (1 year).
The duration of a second class medical, for the exercise of commercial pilot privileges, remains 12 calendar months for all pilot ages. However, pilot under the age of 40 can use his second class certificate as if it was issued as a third class medical for 60 calendar months for exercising private and recreational pilot privileges.
The new rule can be viewed through this link.