The Aircraft Reactor Experiment (ARE) was an attempt by Oak Ridge National Laboratories (ORNL) that began in the 1940s to power an aircraft by means a Molten Salt Reactor (MSR) which is a type of nuclear reactor. This would have given aircraft a much longer flight range due to the higher energy density of nuclear fuels over fossil fuels.
A MSR was selected for this project was because they are small reactors and don't need a containment structure. The ARE never saw completion, but the technology was further explored for electricity production. This resulted in the molten salt reactor experiment which was the first molten salt reactor designed for electricity production. One big factor that contributed to the decision to stop ARE research was the invention of intercontinental ballistic missiles, which meant that explosives could be delivered without the use of an aircraft.