Which of the following items is NOT typically included in an onboard survival kit?

A sleeping bag is not typically included in an onboard survival kit due to space and weight limitations in an aircraft. Moreover, the primary purpose of a survival kit is to provide essential tools and supplies for short-term survival, focusing on immediate needs such as signaling for help, hydration, and shelter from the elements. Flare, water bottle, and tent are all practical items for survival situations, as they serve specific functions—signal for rescue, maintain hydration, and provide temporary shelter. In contrast, a sleeping bag would be less critical, more cumbersome, and not necessary for the initial survival period, especially considering the limited space in an aircraft for carrying additional cargo.