This dataset includes Level 1B (L1B) data products from the MODIS/ASTER Airborne Simulator (MASTER) instrument. The spectral data were collected during two flights aboard a DC-8 aircraft and one flight on a NASA ER-2 aircraft over California, Nevada, and eastern Pacific Ocean on 1999-06-18 to 1999-06-30. The objectives of this deployment included validation and cross-calibration of the instrument on the two airborne platforms. This deployment was coordinated by NASA's Dryden Flight Research Center (DRFC), renamed Armstrong Flight Research Center in 2014, located in Edwards, California. Data products include L1B georeferenced multispectral imagery of calibrated radiance in 50 bands covering wavelengths of 0.460 to 12.879 micrometers at spatial resolution of 7 to 50 meters. The L1B file format is HDF-4. In addition, the dataset includes flight paths, spectral band information, instrument configuration, ancillary notes, and summary information for each flight, and browse images derived from each L1B data file.