A computer-implemented method of predicting aircraft navigation performance, comprising: determining, by one or more computing devices included in an aircraft, that one or more navigational aid measurements are not available to the aircraft; wherein when one or more navigational aid measurements are not available to the aircraft, the method comprises: estimating, by the one or more computing devices, a future actual navigation performance associated with the aircraft for a future point in a flight plan, wherein the future actual navigation performance is based at least in part on data indicative of the flight plan associated with the aircraft and one or more parameters associated with the future point in the flight plan, and includes an estimate of a radial position error; determining, by the one or more computing devices, a future required navigation performance associated with the future point in the flight plan, wherein the future required navigation performance includes a radial position error limit; comparing, by the one or more computing devices, the future actual navigation performance to the future required navigation performance to determine if the future actual navigation performance satisfies the future required navigation performance; providing, by the one or more computing devices to an onboard system of the aircraft, information indicative of whether the future actual navigation performance satisfies the future required navigation performance; and activating, via the onboard system, an alert based on the information indicative of whether the future actual navigation performance satisfy the future required navigation performance. determining, by one or more computing devices included in an aircraft, that one or more navigational aid measurements are not available to the aircraft; wherein when one or more navigational aid measurements are not available to the aircraft, the method comprises: estimating, by the one or more computing devices, a future actual navigation performance associated with the aircraft for a future point in a flight plan, wherein the future actual navigation performance is based at least in part on data indicative of the flight plan associated with the aircraft and one or more parameters associated with the future point in the flight plan, and includes an estimate of a radial position error; determining, by the one or more computing devices, a future required navigation performance associated with the future point in the flight plan, wherein the future required navigation performance includes a radial position error limit; comparing, by the one or more computing devices, the future actual navigation performance to the future required navigation performance to determine if the future actual navigation performance satisfies the future required navigation performance; providing, by the one or more computing devices to an onboard system of the aircraft, information indicative of whether the future actual navigation performance satisfies the future required navigation performance; and activating, via the onboard system, an alert based on the information indicative of whether the future actual navigation performance satisfy the future required navigation performance. estimating, by the one or more computing devices, a future actual navigation performance associated with the aircraft for a future point in a flight plan, wherein the future actual navigation performance is based at least in part on data indicative of the flight plan associated with the aircraft and one or more parameters associated with the future point in the flight plan, and includes an estimate of a radial position error; determining, by the one or more computing devices, a future required navigation performance associated with the future point in the flight plan, wherein the future required navigation performance includes a radial position error limit; comparing, by the one or more computing devices, the future actual navigation performance to the future required navigation performance to determine if the future actual navigation performance satisfies the future required navigation performance; providing, by the one or more computing devices to an onboard system of the aircraft, information indicative of whether the future actual navigation performance satisfies the future required navigation performance; and activating, via the onboard system, an alert based on the information indicative of whether the future actual navigation performance satisfy the future required navigation performance.