  Type Ia supernovae are an important tool for studying the expansion history
of the universe. Advancing our yet incomplete understanding of the explosion
scenario requires detailed and realistic numerical models in order to interpret
and analyze the growing amount of observational data. Here we present first
results of our new NLTE model calculations for the expanding atmospheres of
type Ia supernovae that employ a detailed and consistent treatment of all
important NLTE effects as well as line blocking and blanketing. The comparison
of the synthetic spectra resulting from these models with observed data shows
that the employed methods represent an important step towards a more realistic
description of the atmospheres of supernovae Ia.
