The 5BX (Five Basic Exercises) Plan is an exercise program developed for the Royal Canadian Air Force (RCAF) by Bill Orban in the late 1950s, first published in 1961.

The RCAF asked Orban to develop a fitness program for their pilots, a third of whom were not considered fit to fly at the time. The plan was innovative in two respects. Firstly, it did not require access to specialized equipment. Many RCAF pilots were located in remote bases in northern Canada, with no access to gymnasium facilities, so it was important to offer a means of keeping fit without their use. Secondly, the plan only required 11 minutes per day to be spent on the exercises.

While performing research in Illinois, Orban had noticed that, when testing oxygen intake, long periods of exercise did not necessarily lead to significant improvement. This led him to the conclusion that the intensity of exercise was more important to improving fitness than the amount of time spent on it. This aspect of the plan drew a negative reaction from others in the field but the 5BX program proved its worth in the three years of testing that the RCAF performed before releasing the program..

The 5BX Plan is composed of six charts arranged in increasing order of difficulty. Each chart is composed of five exercises that are performed within 11 minutes. The first 4 basic exercises are Calisthenics and the last an Aerobic exercise. As you progress within the system the number of each type of exercise that must be performed increases and the difficulty of each exercise increases.

The exercises are no longer performed by the service (2008), and are considered unnecessarily hazardous in part because they are unsupervised. Many exercise physiologists consider the sit-up in the higher levels to be capable of causing spinal injury, and therefore unsuitable for an unsupervised program. The sit-up exercise can be replaced with the more modern crunch (exercise)