FTAI Aviation Ltd's stock plummeted 5.91% on Monday's intraday trading session, following a downgrade by Stifel Nicolaus analysts who raised concerns over the company's margins and valuation.

The aircraft lessor's shares fell after Stifel cut its rating on FTAI Aviation to "Hold" from "Buy", citing investor scrutiny on the sustainability of its aerospace margins. This comes after a short seller's report last month questioning the company's financial reporting practices, which FTAI Aviation had dismissed as "without merit" after an internal review.

However, despite lowering the rating, Stifel also raised its price target on FTAI Aviation to $123 from $100, indicating a potential upside of around 4% from current levels. The brokerage noted that while the company delivered strong financial performance in Q4, concerns over margins and valuation remain.