Comparison of iron abundances derived by using ATLAS and GAIA model atmospheres as a function of equivalent width (EW) and line excitation potential (EP). These examples display the results obtained for stars with four different temperatures. Circles and asterisks refer to abundances derived with ATLAS and GAIA models, respectively, while solid and dashed lines represent their mean values. Vertical thick and thin bars in the log n(Fe) vs. EW panels are the standard deviations around the average iron abundances.