The time was actually 4:21 PM (BB got it wrong on the Record Card) because the 4:13 time was simply when the case narrative chose to begin in order to explain what the normal air traffic was doing just before the UFO targets appeared. There never were 2 aircraft interceptors, only 1. The total duration was about 44 minutes, but never any visuals and the reports were not detailed enough to correlate specific ground radar and air radar targets. The UFO was highly maneuverable, made left and right turns, climbed 5,000 feet, accelerated to supersonic speed of about 880 mph thus outperforming the F-86D which could not keep up or overtake the UFO. The F-86D got to within 2-1/2 miles and was within 15 seconds of reaching firing position (and later got actual authorization to fire) when the UFO pulled away and never let the F-86D get that close again.
My revised case summary is as follows:
March 20, 1955. Johnson AFB, Tokyo, Japan. 4:21 p.m. CPS-1 air traffic control radar of the USAF 1954th AACS Sq, Johnson AFB, Tokyo RATCC, detected 4 unidentified targets due N at about 32 miles, then after adjusting manual scan found 16 unidentified targets in 6 separate formations N of base at ranges of about 20 to 28 miles, which slowly moved [about 50 mph] from radar scope azimuth 0° to 20° while heading about 145° over 10 mins until 4:31 p.m. F-86D was scrambled from Yokota AFB (about 30 mi ENE of Tokyo airport and RATCC) at 4:32, piloted by USAF 1st Lt. G. D. Merrick, takeoff at 4:36, heading N (350°) at 10,000 ft then W then S then N on a search pattern [roughly around the Yokota AFB] since ADC control site "Butterfly" at Chiba Peninsula did not detect targets on radar. Meanwhile targets on CPS-1 ground radar had become erratic, leaving trails on radar scope like jet aircraft, then became almost stationary at 4:35. USAF 5th AF went on Yellow Alert due to radar tracks. At about 4:51 the F-86D pilot while heading N on the search pattern detected on airborne radar 2 unidentified targets at 45° azimuth (NE), he turned towards them but lost the targets. Then the F-86D radar picked up another target at 30° at 22 miles and headed towards it on afterburner at about 560 mph, with closure rate 100-175 knots. F-86D got radar lock-on at 15 miles, closed on UFO to closest range 2.5 to 3 miles, was within 15 secs of firing position, dropped afterburner to not overtake too quickly, but UFO began to accelerate to 50 knots faster than the F-86D despite the pilot going on afterburner again. When the UFO pulled out to 7 miles range it made a left turn, the F-86D turned to follow, then the UFO made 90° right turn and F-86D followed, back onto 20° (~N) heading. ADC site "Butterfly" cleared F-86D pilot to fire on the UFO. UFO began climbing while F-86D closed to 5 miles and climbed to 16,000 ft on afterburner to follow, overshot the UFO's leveled off altitude of 15,000 ft then went into a shallow dive back to 15,000 ft reaching Mach 0.98 (~650 mph). UFO then began to pull away to 9 miles range, increasing speed to 200 knots faster than the F-86D [or ~880 mph supersonic], then gradually turning left 45° while pulling away to 15 miles range, breaking the F-86D's radar lock, and pilot broke pursuit at ~5:05 p.m. No visual confirmations, and no direct correlation of ground and air radar targets. (Sparks; Project 1947; NICAP) ~44 mins 2 witnesses ground and air radar