def _apply_scalar_cards(model, model2_renumber):
    """apply cards from model2 to model if they don't exist in model"""
    if model.aero is None and model2_renumber.aero:
        model.aero = model2_renumber.aero
    if model.aeros is None and model2_renumber.aeros:
        model.aeros = model2_renumber.aeros
    model.mkaeros += model2_renumber.mkaeros
    for key, param in model2_renumber.params.items():
        if key not in model.params:
            model.params[key] = param
