MATISSE total flux spectra. Top: L and M band from the UTs (blue) and the ATs (red; GRA4MAT) from epochs 4 and 5, respectively (Table B.1). NEOWISE photometry from 2020 (corrected for saturation) is shown for comparison (green). Bottom: N-band spectrum (black; UTs) against earlier spectra from Spitzer (green; Green et al. 2006), MIDI (red; Quanz et al. 2006), and SOFIA (blue; Green et al. 2016). The flux uncertainty of MATISSE is about 10% for the case of FU Ori (error bar in the lower panel). Spectral regions where atmospheric transmittance hinders terrestrial observations are cut off from the spectra.