In our previous work the model of the electron transport in CNTFETs with extended contacts was developed for equilibrium case using combination of the density-functional theory and equilibrium Green functions formalism. Here we extrapolate it to the case of the arbitrary biased CNTFET using simplest thinkable assumptions, which allows us to calculate drain current as a function of the gate and drain potentials. For Al and Pd electrodes we show qualitative agreement of our model with the existing experimental results both in terms of polarity of the device (p- or n-type FET) and dependence on the contact length. Most of the prediction justified by experimental data were done at ab-initio level for the first time.