  We present our sixth set of results from our mid-infrared imaging survey of
Milky Way Giant HII regions with our detailed analysis of NGC 3603, the most
luminous GHII region in the Galaxy. We used imaging data from the FORCAST
instrument on the Stratospheric Observatory For Infrared Astronomy (SOFIA) at
20 and 37 microns which mapped the central ~8.5'x8.5' infrared-emitting area of
NGC 3603 at a spatial resolution of <~3". Utilizing these SOFIA data in
conjunction with multi-wavelength observations from the near-infrared to radio,
including Spitzer-IRAC and Herschel-PACS archival data, we investigate the
physical nature of individual infrared sources and sub-components within NGC
3603. For individual compact sources we used the multi-wavelength photometry
data to construct spectral energy distributions (SEDs) and fit them with
massive young stellar object (MYSO) SED models, and find 14 sources that are
likely to be MYSOs. We also detect dust emission from the 3 massive proplyd
candidates, as well as from the disk and outflow of the evolved blue
supergiant, Sher 25. Utilizing multi-wavelength data, we derived
luminosity-to-mass ratio and virial parameters for the star-forming clumps
within NGC 3603, estimating their relative ages and finding that NGC 3603 is an
older GHII region overall, compared to our previously studied GHII regions. We
discuss how NGC 3603, which we categorize as a 'cavity-type' GHII region,
exhibits a more modest number of MYSOs and molecular clumps when compared to
the 'distributed-type' GHII regions that share similar Lyman continuum photon
rates.
