also controlled a flight of MiGCAP fighters for unarmed support aircraft operating over the Tonkin Gulf. The EC-121Ds also served as an airborne communications relay center for strike aircraft to transmit mission results and position reports to Danang Air Control Center; directed operations of fighter escorts, MiGCAPs, Lockheed C-130 Hercules flare ships, and A-26 strike aircraft along the North Vietnamese-Laotian border; provided radar and navigational assistance for combat search and rescue missions; and assisted fighters in finding tankers for emergency refueling. The government of China, in May 1966, formally protested an incursion by a Republic F-105 Thunderchief pursuing a North Vietnamese MiG it subsequently shot down 25 miles inside Chinese territory. A US board of inquiry recommended that College Eye also had to monitor the "no-fly zone" inside the North Vietnamese border with China, to provide alerts to US aircraft nearing the buffer zone and to report border crossing violations by US aircraft. This could not be done from the gulf, so a third orbit, Ethan Charlie, was created in Laos. After tests in June and August, regular missions began 24 August. Not enough EC-121s or crews were available to support three orbits twice daily, so the Laotian orbit was only flown every third day, with Ethan Bravo missions cancelled on those days. After 13 October 1966, the Charlie orbit was flown every day and the Bravo orbit suspended altogether. In April 1967, four more EC-121s were deployed, to Thailand on 29 May, making for a total strength of three College Eyes in Taiwan and six in Thailand. In April 1967, USAF began fitting its entire EC-121 fleet with QRC-248 IFF transponder interrogators. QRC-248 had been developed to follow Soviet-export aircraft flown by the Cuban Air Force. The SRO-2 transponders installed in Soviet export MiGs enabled Cuban ground-controlled interception (GCI) radars to identify and control their fighters. A testbed EC-121 called Quick Look had flown with College Eye in January 1967 to test QRC-248 and found that North Vietnamese MiGs used the same transponder. QRC-248 accurately discriminated MiG radar returns from the myriad returns picked up during a mission and extended the range of low-altitude detection to more than 175 miles, covering virtually all important North Vietnamese target areas. By May, all College Eyes had been fitted with QRC-248. Ethan Bravo's mission was changed from that of a backup for Ethan Alpha to being the primary QRC-248 listener, but College