Attorney Martin Woods entered the plea on behalf of 62-year Michael B. Ferrero, who was not present in court.
The California Highway Patrol's air operations unit was on routine patrol along Highway 37 in Sonoma County on Jan. 3 when it spotted a pilot flying recklessly.
CHP officals said the pilot was flying as low as 50 feet above the ground, and within 100 feet of highway traffic.
The plane's tail number was traced to a Penngrove man, the CHP said.
The officers contacted Ferrero when he landed at the Petaluma Municipal Airport and smelled alcohol on his breath, CHP officials said. He was cited for flying under the influence after failing field sobriety tests.
The Sonoma County District Attorney's Office charged Ferrero on Friday with four misdemeanor counts: flying under the influence, flying with a blood-alcohol level greater than 0.04 percent -- the level considered intoxicated while flying -- operating an aircraft in a reckless manner, and operating or maintaining an aircraft under the influence.
Woods said Ferrero "is very sorry he caused concern to anyone who was driving, and never intended to cause anybody concern for their safety."
Ferrero worked in the banking industry and is retired, Woods said.
He said Ferrero may have to serve a 30-day jail sentence if he is convicted, in addition to any penalties imposed by the Federal Aviation Administration, which could include losing his pilot's license.
The penalty for flying under the influence is 30 days to six months in jail and a fine of up to $250, according to the California Public Utilities Code that applies to aviation offenses.
This morning, Judge Bradford DeMeo set a date of March 7 for a settlement conference, but the judge also said he may have to recuse himself from the case.