The majority of ZELL experiments, which including the conversion of several front-line combat aircraft for trialling the system, occurred during the 1950s amid the formative years of the Cold War. As envisioned, the operational use of ZELL would have employed mobile launch platform to disperse and hide aircraft, reducing their vulnerability in comparison to being centralised around established airbases with well-known locations. While flight testing had proved such systems to be feasible for combat aircraft, no ZELL-configured aircraft were ever used operationally. The emergence of ever-capable missiles had greatly reduced the strategic necessity of aircraft for the nuclear strike mission, while questions over practicality had also played a role.