( CNN ) -- President Barack Obama left for Camp David on Marine One Friday but , in a twist that has left some White House reporters scratching their heads , he apparently arrived at the presidential retreat by car . White House Press Secretary Jay Carney explained the decision not to land at Camp David was made in advance because of the weather . Marine One landed at an alternate site near Frederick , Maryland and the president and his daughter , Sasha , rode in a motorcade the rest of way to the compound . Because it is customary practice that the traveling press pool is included whenever the president uses a motorcade , reporters naturally wondered why the pool was not part of the trip or even informed that the president would use a motorcade ahead of time . Meanwhile , CNN 's weather team found no signs of stormy weather in the area at the time Marine One departed the White House . The White House said there were no mechanical issues with the presidential helicopter . `` It was a bit of a surprise because he ( Obama ) usually does not land here . They usually go all the way to Camp David , '' said Kristy Rossignuolo , a customer service representative at the Frederick Municipal Airport . Also Friday , a fighter under the direction of North American Aerospace Defense Command ( NORAD ) intercepted an aircraft in the vicinity of Camp David . The civilian aircraft left the restricted area and landed at the Martinsburg Airport in West Virginia , NORAD said . No other details were immediately available on the incident , which was separate from the decision to divert Marine One . CNN 's Jessica Yellin and John Branch contributed to this report .
NEW : In a separate incident , NORAD intercepts an aircraft in the vicinity of Camp David . Obama left for Camp David on the presidential helicopter but apparently arrived by car . Marine One was reportedly diverted because of bad weather . CNN 's weather team found no signs of stormy weather in the area .