Fearnley Securities has downgraded shares of AP Moller-Maersk as it sounded a note of caution for container lines riding a strong rebound from lockdown lows earlier this year.

The Norwegian investment bank see challenges ahead, despite booming rates and improved volumes.

Fearnley said freight rate expectations based on the Shanghai Shipping Exchange's Shanghai Container Freight Index (SCFI) and China Container Freight Index (CCFI) could "prove lofty."