The development of liquid fire depends mainly on fuel evaporation and heat feedback of flame configuration which are both influenced by the ambient winds. In current work, the height of pioneering flame in the process of flame spread above the surface of jet fuel is measured inside a bench-scale air flow tunnel. The longitudinal air flow velocities are 0.45, 0.88, 1.3, 1.73, 2.15 and 2.57 m/s for both concurrent and opposed flame spreads. Five oil pans with the same length of 100 cm but different widths of 4, 8, 12, 16 and 20 cm are utilized. The experimental results of flame heights considerably deviate from the calculations of classic Thomas model and Oka et al. model. Then, the new-proposed non-dimensional parameter, characteristic size ratio of pool lambda = d/D is introduced into Thomas' model and Oka et al.'s model respectively. The measured flame heights follow well with the improved models H/d = a((m) over dot*)(eta)(u*)(b)lambda(c) and H/d = alpha(Fr-2/3/(Q) over dot*)(beta) lambda gamma, regardless of direction of air flow. The values of empirical coefficients and exponents of the correlations a, b, c, eta in improved Thomas model and alpha, beta and gamma in improved Oka et al. model are derived from the experimental results.