The estimation of loads acting on an aircraft structure is an indispensable task ranging from conceptual, preliminary, and detail design to loads flight testing when an aircraft is already in service. Work package 4 of the DLR project iLOADS covers the range broadly. Physics-based loads and aerodynamic performance analysis methods in pre-design are presented using a parameterized and automatized process nested in an overall aircraft design loop. Such process can be used for conventional an unconventional configurations. Covering the complete design process, a parametric set-up for structural modeling, estimation of loads and loads flight testing for the DLR HALO, a modified Gulfstream G550, is also shown. Finally the in-flight system identification activities including flight tests for the DLR Discus-2c are described.