English: Airy distribution ${\displaystyle A'_{\rm {trans}}}$ (solid lines), corresponding to light transmitted through a Fabry-Pérot resonator, calculated for different values of the reflectivities ${\displaystyle R_{1}=R_{2}}$, and comparison with a single Lorentzian line (dashed lines) calculated for the same ${\displaystyle R_{1}=R_{2}}$.^[1] At half maximum (black line), with decreasing reflectivities the FWHM linewidth ${\displaystyle \Delta \nu _{Airy}}$ of the Airy distribution broadens compared to the FWHM linewidth ${\displaystyle \Delta \nu _{c}}$ of its corresponding Lorentzian line: ${\displaystyle R_{1}=R_{2}=0.9,0.6,0.32,0.172}$ results in ${\displaystyle \Delta \nu _{Airy}/\Delta \nu _{c}=1.001,1.022,1.132,1.717}$, respectively.