Guess they were just low on beer. Airplanes Enter Camp David Airspace Mon Jul 1, 9:07 AM ET By JERRY ESTILL, Associated Press Writer WASHINGTON (AP) - Air Force jets scrambled twice over the weekend to intercept small airplanes making what turned out to be at least three harmless intrusions into the airspace over Camp David while President Bush ( news - web sites) was at the Maryland mountain retreat. In addition, the Secret Service ( news - web sites) said a light plane slipped slightly into the 30-mile-diameter restricted airspace over downtown Washington before correcting itself and continuing on a proper course. The intrusions occurred at a time of heightened national alert for possible terrorist attacks during the July Fourth holiday period. The most dramatic incident occurred at about 10 a.m. Saturday when two fighters thundered in low circles above Winchester, Va. â€” a city of 25,000 about 60 miles south of Camp David â€” until an errant, four-seat Beech A-23 that had failed to heed radio calls landed. "There was a lot of concern when they saw the F-16s flying over Winchester" said Serena Manuel, executive director and manager of Winchester Regional Airport. "There were a lot of people calling about it." Almost exactly 24 hours later, the pilot of a small Cessna plane that ventured into restricted airspace around the presidential retreat in the Catoctin Mountains of Maryland was told to land â€” and did so at Frederick, Md., without a military escort, the Secret Service said. In a third incident, one or two ultralight planes got too close Saturday afternoon and prompted a visit by fighters. However, the military pilots were not able to see anything when they arrived. Authorities determined upon questioning that the ultralight pilot they saw land at the Carroll Valley airport in southern Pennsylvania probably was not the same one tracked flying low and slow over the restricted zone surrounding Camp David. Secret Service spokesman Jim Mackin said Sunday evening that the recreational ultralight flights are common in the scenic area â€” at the northern end of the Shenandoah Valley â€” and that authorities were still trying to determine what became of the one that got away. The three pilots who were questioned by Secret Service agents all were determined to have made inadvertent intrusions and were sent on their way, Mackin said, albeit not without the possibility of facing administrative sanctions by the Federal Aviation Administration ( news - web sites). Mackin emphasized that none of the incidents are taken lightly and that every pilot involved in an intrusion is questioned. But he estimated that at least a couple of dozen incidents have occurred around Camp David and Washington since Sept. 11, although most have gone unreported and have not resulted in fighter jets being scrambled. The incident Saturday morning came less than three hours after Bush had undergone a routine colon screening and was getting ready for a walk. But there was no suggestion of any threat to the president, nor was it known whether he was even aware of the straying planes. The president and first lady Laura Bush ( news, bio, voting record) returned to the White House on Sunday afternoon. FAA spokesman Hank Price said the Beech A-23 aircraft was intercepted at 4,500 feet about 15 miles from Frederick, Md., and escorted to Winchester, where airport officials said they understood the aircraft had entered deeply into the restricted airspace around Camp David. "We can't verify that," Price said. Likewise, the Secret Service declined to say how close the plane came to the presidential compound. Manuel and David Foley, operations supervisor at the Winchester airport, said they believed the Beech plane had entered deeper into the restricted airspace than two other aircraft that had been directed to Winchester since the Sept. 11 terrorist attacks. "I don't know if he got right over," Foley said. "I think he knew he messed up pretty badly." He said he believed the pilot and passenger were en route from New York City to Las Vegas. Manuel added that the pilot was thrown off course by cloud cover. On June 19, a pilot flew a single-engine Cessna into restricted airspace a few miles from the White House. He was escorted to Richmond International Airport and faces FAA sanctions, but was not charged with a crime. ___ Associated Press writer Steve Szkotak in Richmond, Va., contributed to this report.