Quantitative spectroscopy of hot stars: accurate atomic data applied on a large scale as driver of recent breakthroughs

OB-type stars present hotbeds for non-LTE physics because of their strong radiation fields that drive the atmospheric plasma out of local thermodynamic equilibrium. We report on recent breakthroughs in the quantitative analysis of the optical and UV-spectra of OB-type stars that were facilitated by application of accurate and precise atomic data on a large scale. An astrophysicist's dream has come true, by bringing observed and model spectra into close match over wide parts of the observed wavelength ranges. This allows tight observational constraints to be derived from OB-type stars for a wide range of applications in astrophysics. However, despite the progress made, many details of the modelling may be improved further. We discuss atomic data needs in terms of laboratory measurements and also ab-initio calculations. Particular emphasis is given to quantitative spectroscopy in the near-IR, which will be the focus in the era of the upcoming extremely large telescopes.