An aircraft display system, comprising: a display device; and a processor in operable communication with the display device and adapted to receive at least data representative of a desired course of the aircraft, data representative of required navigation performance for the aircraft, and data representative of estimated position uncertainty for the aircraft, the processor configured, in response to at least these data, to render a horizontal situation indicator on the display device that includes: (i) an aircraft symbol representative of a top-down view of the aircraft, the aircraft symbol rendered at a position that is representative of the actual aircraft position relative to the desired course, wherein the aircraft symbol is rendered at a position relative to the desired course for a current segment of an aircraft flight plan, (ii) an EPU graphic representative of the EPU for the aircraft, the EPU graphic comprising a pair of line segments (215-1, 215-2) symmetrically disposed on either side of the aircraft symbol and separated from each other by a separation distance that is proportional to the EPU for the aircraft, one line segment rendered left of the aircraft symbol, and another line segment rendered right of the aircraft symbol, and (iii) an RNP boundary graphic representative of at least one RNP boundary for the aircraft, the RNP boundary graphic rendered at a position relative to the aircraft symbol and comprising a shaded region that shades a portion of the display device outside the at least one RNP boundary; wherein the processor is configured to determine if the aircraft is experiencing a right lateral deviation and, in response thereto, the RNP boundary graphic comprises only a right RNP boundary. a display device; and a processor in operable communication with the display device and adapted to receive at least data representative of a desired course of the aircraft, data representative of required navigation performance for the aircraft, and data representative of estimated position uncertainty for the aircraft, the processor configured, in response to at least these data, to render a horizontal situation indicator on the display device that includes: (i) an aircraft symbol representative of a top-down view of the aircraft, the aircraft symbol rendered at a position that is representative of the actual aircraft position relative to the desired course, wherein the aircraft symbol is rendered at a position relative to the desired course for a current segment of an aircraft flight plan, (ii) an EPU graphic representative of the EPU for the aircraft, the EPU graphic comprising a pair of line segments (215-1, 215-2) symmetrically disposed on either side of the aircraft symbol and separated from each other by a separation distance that is proportional to the EPU for the aircraft, one line segment rendered left of the aircraft symbol, and another line segment rendered right of the aircraft symbol, and (iii) an RNP boundary graphic representative of at least one RNP boundary for the aircraft, the RNP boundary graphic rendered at a position relative to the aircraft symbol and comprising a shaded region that shades a portion of the display device outside the at least one RNP boundary; wherein the processor is configured to determine if the aircraft is experiencing a right lateral deviation and, in response thereto, the RNP boundary graphic comprises only a right RNP boundary. (i) an aircraft symbol representative of a top-down view of the aircraft, the aircraft symbol rendered at a position that is representative of the actual aircraft position relative to the desired course, wherein the aircraft symbol is rendered at a position relative to the desired course for a current segment of an aircraft flight plan, (ii) an EPU graphic representative of the EPU for the aircraft, the EPU graphic comprising a pair of line segments (215-1, 215-2) symmetrically disposed on either side of the aircraft symbol and separated from each other by a separation distance that is proportional to the EPU for the aircraft, one line segment rendered left of the aircraft symbol, and another line segment rendered right of the aircraft symbol, and (iii) an RNP boundary graphic representative of at least one RNP boundary for the aircraft, the RNP boundary graphic rendered at a position relative to the aircraft symbol and comprising a shaded region that shades a portion of the display device outside the at least one RNP boundary; wherein the processor is configured to determine if the aircraft is experiencing a right lateral deviation and, in response thereto, the RNP boundary graphic comprises only a right RNP boundary.