How often is a biannual flight review required after not flying for 2 years?

A biannual flight review, also known as a BFR, is required every two years for a pilot to maintain their proficiency and currency. The key point here is that the term "biannual" refers to an interval of two years. If a pilot has not flown for two years, they must complete a flight review before they can act as pilot-in-command of an aircraft. This review ensures that pilots remain competent in their flying skills and are updated on any new regulations or procedures that may have been introduced during their absence from flying.

While it is important for pilots to remain current and regularly fly, the specific regulation states that the flight review must occur every two years, making this answer the correct interpretation of the requirement.