A system to determine aircraft fuel mileage performance, comprising: a memory; a processor disposed in communication with said memory, and configured to issue a plurality of instructions stored in the memory, wherein the instructions issue signals to: receive real-time aircraft data during aircraft flight; process said real-time data to determine real-time aircraft mass data; and calculate a real-time fuel mileage performance for the aircraft based upon determined aircraft mass data; the system further comprising means for deciding on adjusting an altitude and a cruise speed of said aircraft based on said fuel mileage performance, wherein said instructions stored in memory further causes said processor to calculate a fuel mileage performance based on said mass data and at least one parameter from the group of parameters consisting of: an environmental parameter, and a performance parameter, and wherein the performance parameter includes speed data, altitude data, temperature data, pressure data, and angle of attack data. a memory; a processor disposed in communication with said memory, and configured to issue a plurality of instructions stored in the memory, wherein the instructions issue signals to: receive real-time aircraft data during aircraft flight; process said real-time data to determine real-time aircraft mass data; and calculate a real-time fuel mileage performance for the aircraft based upon determined aircraft mass data; the system further comprising means for deciding on adjusting an altitude and a cruise speed of said aircraft based on said fuel mileage performance, wherein said instructions stored in memory further causes said processor to calculate a fuel mileage performance based on said mass data and at least one parameter from the group of parameters consisting of: an environmental parameter, and a performance parameter, and wherein the performance parameter includes speed data, altitude data, temperature data, pressure data, and angle of attack data. receive real-time aircraft data during aircraft flight; process said real-time data to determine real-time aircraft mass data; and calculate a real-time fuel mileage performance for the aircraft based upon determined aircraft mass data; the system further comprising means for deciding on adjusting an altitude and a cruise speed of said aircraft based on said fuel mileage performance, wherein said instructions stored in memory further causes said processor to calculate a fuel mileage performance based on said mass data and at least one parameter from the group of parameters consisting of: an environmental parameter, and a performance parameter, and wherein the performance parameter includes speed data, altitude data, temperature data, pressure data, and angle of attack data. determined aircraft mass data; the system further comprising means for deciding on adjusting an altitude and a cruise speed of said aircraft based on said fuel mileage performance, wherein said instructions stored in memory further causes said processor to calculate a fuel mileage performance based on said mass data and at least one parameter from the group of parameters consisting of: an environmental parameter, and a performance parameter, and wherein the performance parameter includes speed data, altitude data, temperature data, pressure data, and angle of attack data.