NOx‐catalyzed production of ozone over large regions of North America and Europe is a serious air quality problem that often involves biogenic hydrocarbons, mainly isoprene. Peroxy‐methacrylic nitric anhydride (MPAN, CH2C(CH3)C(O)OONO2) is formed uniquely from isoprene‐NOx photochemistry hence is an indicator of recent ozone production from isoprene. Presented here are the first airborne measurements of MPAN along with PAN (peroxyacetic nitric anhydride, CH3C(O)OONO2), PPN (peroxypropionic nitric anhydride, CH3CH2C(O)OONO2) and ozone measurements. Relationships between these species are used to estimate the contributions of anthropogenic and biogenic hydrocarbons (BHC) to regional tropospheric ozone production, providing direct evidence of ozone production from BHC‐NOx photochemistry.