The RAF fleet size assumes a risk of "on average one (F-35) aircraft loss every 30,000 hours", according to Minister for Defence Procurement Jeremy Quin.
That length of time equates to just under three and a half years.
Mr Quin was answering a parliamentary question from Conservative MP Mark Francois about the estimate he has made in relation to the future loss rates of the F-35 aircraft.
This line of questioning comes after a British F-35B, worth roughly £88.8m, embarked on Royal Navy aircraft carrier HMS Queen Elizabeth, crashed during flying operations over the Mediterranean last month.
A joint UK-US operation was launched to retrieve the jet after the incident.
The wreckage of the Lighting aircraft has been located by experts, but not yet recovered from the ocean, MPs were told last week.