leading "Paula" flight, in gun-equipped F-4Es instead of the Combat Tree F-4Ds they usually flew, on a MiGCAP to cover the exit of the strike force. While they were west of Phu Tho and south of Yen Bai, the EC-121 vectored them to intercept MiG-21s returning to base after damaging one of the US chaff escorts. The MiGs were still approximately away and Ritchie turned the flight south to cross the Black River. As they closed, Disco gave them warning that the MiG return had "merged" with the Paula flight's return on his screen. Ritchie reversed course, observed the first MiG at his 10 o'clock position and turned left to meet it head-on. When Ritchie passed the first MiG-21, he recalled the engagement of May 10 and waited to see if there was a trailing MiG. When he observed the second MiG, which he also passed head-on, he reversed hard left to engage. The MiG turned to its right to evade the attack, an unusual maneuver, and Ritchie used a vertical separation move to gain position on its rear quarter. DeBellevue obtained a solid boresight (dogfighting radar lock) on it while at the MiG's 5 o'clock; although fired from the edge of their flight envelopes, both AIM-7s struck home. The first MiG had also turned back and was attacking the last F-4 in Ritchie's flight from behind, an often fatal consequence to US aircraft employing the then-standard "fluid four" tactical formation. Ritchie made a hard turn across the curving intercept of the MiG, again coming out at its 5 o'clock, and the MiG, apparently perceiving the threat, broke hard right and dove away. Ritchie fired an AIM-7 from inside its minimum range and at the limit of its capability to turn. Expecting the Sparrow to miss, he was trying to switch to a gun attack in the relatively unfamiliar F-4E he was flying that day when the missile exploded the MiG, 1 minute and 29 seconds after the first kill. A competition to become the Air Force's first Vietnam ace developed between Ritchie and Captain Jeffrey S. Feinstein of another of the 432nd's squadrons, the 13th TFS, who scored his 3rd and 4th kills on July 18 and July 29. Each had a claim denied by Seventh Air Force's Enemy Aircraft Claims Evaluation Board, Ritchie and DeBellevue for a claim of a MiG-21 on June 13, and Feinstein for a