On December 4, 2010, about 2121 central standard time, a Boeing 747-47UF airplane, N499MC, operated by Atlas Air Inc. as flight 7552 sustained minor right wing damage when it struck the horizontal stabilizer of a standing Bombardier Inc CL-600-2C10 airplane, N502MJ, operated by Mesa Airlines Inc. as flight 7246. N499MC was taxiing for takeoff and N502MJ was holding short of its gate area at the Chicago O'Hare International Airport (ORD), Chicago, Illinois. N502MJ sustained substantial damage to its horizontal stabilizer. There were no reported injuries to the 4 flight crewmembers on N499MC, or to the 2 pilots, 2 flight attendants, and 29 passengers on N502MJ. Night visual meteorological conditions prevailed and instrument flight rules flight plans were filed and activated for both flights. The Atlas Air flight was conducted under 14 Code of Federal Regulations Part 121 as a non-scheduled domestic cargo flight and the Mesa Airlines Inc. flight was conducted under 14 Code of Federal Regulations Part 121 as a scheduled domestic passenger flight. N499MC was originating from ORD at the time of the accident and was destined for the Toledo Express Airport, near Toledo, Ohio. N502MJ originated from the Charlotte/Douglas International Airport, near Charlotte, North Carolina, about 1905, and was destined for ORD. The Mesa Airlines captain stated that after landing the flight was directed to taxi to gate C-4. The flightcrew contacted C-ramp control and the CL-600-2C10 regional jet was cleared to taxi into gate area and hold short. The captain reported that the regional jet was taxied up on the C-4 gate line and the flightcrew waited to be marshaled in. The flightcrew noticed the 747 taxiing behind their airplane, felt the airplane rock, and thought it was jet blast. The ramp personnel who parked the regional jet advised its flightcrew of the contact with the 747. The flightcrew exited the airplane and observed the substantial damage on the lower side of the regional jet’s right horizontal stabilizer. The crew subsequently advised an air traffic controller that the Atlas Air 747 struck the regional jet with its wing. The Atlas Air captain reported that while taxiing on taxiway A7, they approached a parked regional jet on their right. The captain asked the first officer to check wing tip clearance. The first officer responded that clearance existed between the airplanes. The captain replied that the Atlas Air flight would deviate slightly left of centerline for extra clearance. An air traffic controller subsequently informed the Atlas Air flight that a regional jet had reported being struck by the 747. The Atlas Air flight taxied to T10 pad and airport rescue and firefighting personnel observed the right winglet to be damaged. The Atlas Air first officer stated that the captain asked him to see if they had clearance from the regional jet that was parked abeam taxiway A7. The first officer indicated that based on the time of the night, conditions of the field, and the lighting, he thought they had enough clearance to taxi by that regional jet. The first officer reported this flight was his initial operating experience out of ORD. A flightcrew member in the outboard jumpseat reported that the flightcrew felt the airplane shutter. He stated that that the captain attributed it to jet blast from the 767 airplane that the flight was following. The 747-47UF airplane’s wingspan, dependant on fuel loading, is between 211 feet 5 inches and 213 feet. The overall length of the CL-600-2C10 airplane is 106 feet 8 inches. From aerial images of taxiway A abeam gate C-4, the distance from the centerline of taxiway A northeast to its dashed edgeline is about 38 feet and the distance from the centerline of taxiway A northeast to the non-movement area markings is about 129 feet. Mesa Airlines supplied flight data recorder (FDR) data from the accident flight. A video from an airport camera of the C-4 gate area was reviewed. Both the video and FDR data revealed that the regional jet was standing when it was impacted by the 747 that taxiing on the A7 taxiway. The Federal Aviation Administration Aeronautical Information Manual (AIM), Chapter 2 - Aeronautical Lighting and Other Visual Aids, section 3 – Airport Marking Aids and Signs, sub-section 2-3-4 – Taxiway Markings, in part, stated: b. Taxiway Centerline. 1. Normal Centerline. The taxiway centerline is a single continuous yellow line, 6 inches (15 cm) to 12 inches (30 cm) in width. This provides a visual cue to permit taxiing along a designated path. Ideally, the aircraft should be kept centered over this line during taxi. However, being centered on the taxiway centerline does not guarantee wingtip clearance with other aircraft or other objects. FAA 14 Code of Federal Regulations part Part 91 – General Operating and Flight Rules, subpart 91.113 – Right-of-way Rules, in part, stated: (b) General. When weather conditions permit, regardless of whether an operation is conducted under instrument flight rules or visual flight rules, vigilance shall be maintained by each person operating an aircraft so as to see and avoid other aircraft.