The probation was lifted early, however, by new Secretary of Defense Leon Panetta last month. In his decision, Panetta said there was "real progress towards fixing some of the known problems that we had with STOVL."
"We now believe... that the STOVL variant is demonstrating the kind of performance and maturity that is in line with the other two variants of the JSF," Panetta said.
Two top-ranking senators on the Senate Armed Services Committee, Sen. John McCain (R.-Arizona) and Sen. Carl Levin (D.-Michigan), reportedly penned a letter to Panetta in which they questioned his decision on the same day Kendall shared his thoughts on the F-35 program.
"When Secretary Gates originally decided to put the F-35B on probation, he intended his decision to invoke specific courses of action by Lockheed Martin and the program management office to help ensure that the F-35B program established technical maturity and design stability in several key areas. Have these actions been taken?" the two wrote Monday, according to Defense News. "If not, your decision may have foregone a valuable opportunity to continue driving desired improvements through the still-nascent, enormously challenging program to develop the F-35B."
A spokesperson for the Marine Corps did not immediately respond to a request for comment concerning the letter from McCain and Levin.