The Utah Civil Air Patrol planned to go back to square one Saturday in its search for a missing Arizona man and his son whose airplane failed to complete a scheduled flight to Chandler, Ariz.

Lt. Col. Jerry Wellman, a spokesman for the Utah CAP, said 27 search flights were launched Friday but failed to turn up any sign of the missing aircraft. An Arizona CAP helicopter was sent to the Grand Canyon following a possible sighting Friday, but all that was found was evidence of a lightning strike.Wellman said good weather anticipated for Saturday should allow CAP wings in both Utah and Arizona to mount a full-scale effort with every available plane in the air. He said officials remain optimistic and are hoping that Sherman Flake, 52, and his 19-year-old son, Scott, managed to set the aircraft down safely and are just unable to signal to passing search planes.

The Flakes were last seen about 10 a.m. Wednesday when they landed on a road near Fillmore and taxied up to a convenience store and refueled their aircraft. They had left Burley, Idaho, earlier that morning on a flight to Chandler. Wellman said the Flakes told the store clerk that they were on their way to Chandler, so officials are concentrating search efforts on the premise that there has been no deviation in the original plan.

CAP units will first follow the two most likely flight routes, one following I-15 to Hurricane and then southeast over the Grand Canyon, and the second following U.S. 89 south to Page, Ariz.

Wellman said residents along the two possible flight routes are urged to contact the CAP at the Salt Lake City office, 533-5456, if they spotted anything unusual about aircraft passing their areas on Wednesday.