A series of numerical simulations of R134a flow boiling in two small tubes with inner diameters of 1 and 2.17 mm under high flight acceleration were conducted based on the VOF model. Six acceleration levels from 1 to 15 g and three directions from 0° to 180° were investigated. At first, the simulated frictional pressure drops under low flight acceleration are compared with previous experimental findings, and the comparison results show a consistent trend. Then, the simulated flow patterns and pressure drops under high flight acceleration with different levels and directions are intercompared, and the influences of high flight acceleration are obtained. The intercomparison results reveal that the flow patterns and pressure drops are influenced by high flight acceleration dramatically. The total and frictional pressure drops decrease with the increasing flight acceleration at θ = 0°, decrease slightly at θ = 90°, and increase at θ = 180°, monotonically, because of the variation of flow patterns. The vapor phases gradually turn into quasi-ellipsoids/spheres, quasi-stratified state, and elongated slugs at θ = 0°, 90°, and 180°, respectively, as the flight acceleration increases.