Blakeslee flew the P-51 Mustang for the first time in December 1943 and thereafter worked hard to have the 4th FG re-equipped as soon as possible with the new fighter, pushing hard, especially as he now became commanding officer of the 4th on January 1, 1944. The 8th Air Force Command eventually agreed to the request, provided the pilots were operational on the P-51 within 24 hours of receiving them. Blakeslee agreed, instructing his pilots to "learn how to fly them on the way to the target".