Approximate analytical solutions for the wetting kinetics of thin films pinned to a slot have been obtained for both when the flow is driven by surface tension and when it is driven by disjoining pressure due to the London-van der Waals forces. The two expressions for wetting kinetics were patched to provide an overall solution that shows that the transition from surface tension driven flow to disjoining pressure driven flow takes place at extraordinarily large times. Numerical solutions are next presented to show that the transition indeed takes place at large times but not as large as that predicted by patching. The mechanism as to why this takes place is discussed.