Extra diligence is necessary when transiting the Chino Airport (CNO) Class D airspace due to the proximity of the Ontario International Airport (ONT) Class C airspace.

Aircraft departing CNO runways 26L/R via a north (right traffic) downwind or aircraft transitioning East/Westbound transitions from the Northside of CNO occasionally make an unexpected maneuver South, off the downwind leg, to remain clear of the portion of ONT Class C airspace adjacent to CNO Class D airspace.  Pilots avoiding this portion of the ONT Class C airspace are crossing the CNO runway 26L/R final approach course, creating traffic conflictions with landing aircraft.

CNO Tower has an agreement with Southern California TRACON to utilize the ONT Class C airspace, 2500' MSL and below, within the highlighted portion of the attached graphic.  Pilots in communication with CNO Tower are authorized to transition the ONT Class C airspace within the highlighted area.  Riverside Drive is the visual boundary between ONT Class C Airspace and CNO Class D Airspace.  Pilots should remain South of Riverside Drive while in communication with CNO ATCT transiting Eastbound.

The graphic below illustrates the specific area of airspace ONT Tower has granted to CNO Tower for transitioning aircraft that are in communication with CNO Tower. 

CNO Tower strongly recommends all aviators departing CNO runways 26L/R on a right downwind departure or transitioning eastbound, to remain on course and in communication with the CNO tower until advised.

When CNO tower is closed, the agreement between CNO tower and Southern California TRACON (SCT) is NOT in effect. Aircraft intending to make a right downwind departure when CNO tower is closed are required to remain outside of the ONT Class C airspace.  For transition through ONT Class C airspace, aviators are required to contact SCT to coordinate their transition request.