Explanation: This is in reference to an infamous friendly-fire incident early during the War in Afghanistan, wherein a US pilot on a 'go-pill' attacked some allied Canadian troops after mistaking them for hostiles, causing the first Canadian deaths of the war. Spurred in no small part by said incident, amphetamines are no longer approved as 'go-pills' for US pilots.
Traditionally, 'go-pills' (often amphetamines, but usually not methamphetamine) have been used to induce alertness in pilots called for a sortie on short-notice since WW2. The thinking being that being exhausted and drowsy is a bigger danger than being a little 'keyed up' when it comes to flying into a warzone. However, the increased danger of friendly fire incidents with effective CAS and need for careful distinction between similar-looking targets has decreased the efficacy of such 'traditional' methods, as seen by the mentioned friendly-fire incident in Afghanistan.