This article presents a direct and analytical method in the conceptual design phase of aircraft for the initial estimation of air taxi jet takeoff weight using simultaneous application of various aircraft design methods including Roskam, Raymer, and Jenkinson. To achieve this objective, Roskam's aircraft initial weight estimation relationships are employed and combined with the existing relationships in Raymer and Roskam methods for specific fuel consumption during cruise and loiter phases, as well as the relationships available in Jenkinson's method for the ratio of operational empty weight to takeoff weight as a function of aircraft range, yielding a direct relationship for calculating aircraft takeoff weight. The proposed method was validated using 10 actual air taxi aircraft (6-20 passengers), demonstrating an average error of 0.81%, which is approximately four times more accurate than Roskam (3.26%) and Raymer (3.82%) methods. Using the proposed analytical method, due to the elimination of trial-and-error procedures or solving nonlinear equations, the accuracy and speed of initial aircraft weight estimation is enhanced.