Which of the following actions is NOT a method of addressing frost accumulation on an aircraft?

Allowing frost to remain until takeoff is a method that can compromise safety and performance, making it the correct answer to the question. Frost on aircraft surfaces, especially on wings and control surfaces, disrupts the airflow and can lead to increased drag, decreased lift, and potential stalls. Therefore, it is necessary to ensure that surfaces are clear before flight.

In contrast, the other options are appropriate and standard methods for dealing with frost. The application of deicing fluids is a common and effective method for removing frost from aircraft surfaces, providing a layer to prevent further accumulation and ensuring a clean surface for optimal aerodynamic performance.

Waiting for natural sunlight can also be effective, as the heat from the sun may help melt frost, especially during daylight operations. Using a heat source is yet another method, as airflow from the engines or electric heat from heaters can assist in melting away frost. Each of these methods serves to enhance safety and ensure safe takeoff conditions, which is why they are valid techniques for addressing frost accumulation.