  We present results of spectrometric studies based on the observations of very
strong 3C 279 flares in high and very-high-energy bands and discuss their
implications regarding the origin of radiation mechanisms. The FSRQ 3C 279
(z=0.536) is one of the most luminous gamma-ray emitting AGN. It shows
variability on time scales down to minutes during strong flares detected by the
Fermi-LAT. We have analyzed LAT and Swift-XRT data for the flaring periods in
June 2015 and January 2018, when the flux above 100 MeV during hourly time
intervals could exceed $3 \times 10^{-5}$ ph cm$^{-2}$ s$^{-1}$. The X-ray flux
derived from Swift X-ray observations described by a very hard spectrum with
photon index ~1.5 is typically explained by Inverse Compton scattering of low
energy electrons and protons. Here we consider an alternative interpretation
which describes the entire band from X-ray to very high energy as a results of
synchrotron emission by ultra relativistic electrons or protons.
