Yesterday (21 April), the Rolls-Royce (LSE: RR.) share price tanked. While the FTSE 100 index lost 1%, shares in the aircraft engine powerhouse fell 6.5%.

Personally, I wasn’t so surprised by this outsized drop as it was related to a risk I’ve been warning investors about recently. This risk is the main reason I’m not buying Rolls-Royce shares for my portfolio… yet.

Why did the share price plummet?

The 6.5% fall yesterday wasn’t due to any news from the company. Instead, it was related to Q1 earnings from rival GE Aerospace.

GE’s earnings were actually quite strong. Revenue was up 29% on an adjusted basis while adjusted earnings per share was up 25%.

However, on the…