A method of computing and outputting of an uncertainty in a time of arrival of an aircraft at a point along a track, said method comprising: receiving a required time of arrival at a predetermined waypoint; determining a forward late time profile representing the latest time the aircraft could arrive at a point along the track and still arrive at the predetermined waypoint while transiting at a minimum available speed; determining a forward early time profile representing the earliest time the aircraft could arrive at a point along the track and still arrive at the predetermined waypoint while transiting at a maximum available speed; determining a backward early time profile using a maximum speed profile backward from the RTA at the predetermined waypoint, wherein the maximum speed profile is determined for the aircraft while transiting at a maximum available speed; determining a backward late time profile using a minimum speed profile backward from the RTA at the predetermined waypoint, wherein the minimum speed profile is determined for the aircraft while transiting at a minimum available speed; determining a deceleration between the maximum available speed of the forward early time profile to the minimum available speed of the backward late time profile; determining an acceleration between the minimum available speed of the forward late time profile to the maximum available speed of the backward early time profile; determining a moving earliest allowable time defining the earliest time of arrival that can be allowed at a point along the track while enabling arrival of the aircraft at the predetermined waypoint at the RTA, said time being defined by the forward early time profile prior to the start of the determined deceleration, a deceleration time profile between the start and the end of the determined deceleration, and the backward late time profile after the end of the determined deceleration; determining a moving latest allowable time defining the latest time of arrival that can be allowed at a point along the track while enabling arrival of the aircraft at the predetermined waypoint at the RTA, said time being defined by the forward late time profile prior to the start of the determined acceleration, an acceleration time profile between the start and the end of the determined acceleration, and the backward early time profile after the end of the determined acceleration; determining an estimated time uncertainty for each of the forward late time profile, the forward early time profile, the backward early time profile and the backward late time profile; outputting the earliest allowable time, the latest allowable time, the forward late time profile, the forward early time profile, the backward early time profile and the backward late time profile, with the respective determined estimated time uncertainty. receiving a required time of arrival at a predetermined waypoint; determining a forward late time profile representing the latest time the aircraft could arrive at a point along the track and still arrive at the predetermined waypoint while transiting at a minimum available speed; determining a forward early time profile representing the earliest time the aircraft could arrive at a point along the track and still arrive at the predetermined waypoint while transiting at a maximum available speed; determining a backward early time profile using a maximum speed profile backward from the RTA at the predetermined waypoint, wherein the maximum speed profile is determined for the aircraft while transiting at a maximum available speed; determining a backward late time profile using a minimum speed profile backward from the RTA at the predetermined waypoint, wherein the minimum speed profile is determined for the aircraft while transiting at a minimum available speed; determining a deceleration between the maximum available speed of the forward early time profile to the minimum available speed of the backward late time profile; determining an acceleration between the minimum available speed of the forward late time profile to the maximum available speed of the backward early time profile; determining a moving earliest allowable time defining the earliest time of arrival that can be allowed at a point along the track while enabling arrival of the aircraft at the predetermined waypoint at the RTA, said time being defined by the forward early time profile prior to the start of the determined deceleration, a deceleration time profile between the start and the end of the determined deceleration, and the backward late time profile after the end of the determined deceleration; determining a moving latest allowable time defining the latest time of arrival that can be allowed at a point along the track while enabling arrival of the aircraft at the predetermined waypoint at the RTA, said time being defined by the forward late time profile prior to the start of the determined acceleration, an acceleration time profile between the start and the end of the determined acceleration, and the backward early time profile after the end of the determined acceleration; determining an estimated time uncertainty for each of the forward late time profile, the forward early time profile, the backward early time profile and the backward late time profile; outputting the earliest allowable time, the latest allowable time, the forward late time profile, the forward early time profile, the backward early time profile and the backward late time profile, with the respective determined estimated time uncertainty.