Shares of United Parcel Service Inc. and FedEx Corp. experienced a significant decline following an analyst's report detailing Amazon.com Inc.'s aggressive expansion into third-party shipping. Amazon is reportedly leveraging its vast logistics network to offer delivery services that are both cost-effective and rapidly improving in speed.

This development signals a growing competitive threat to the established package delivery giants. The e-commerce behemoth's entry into this market is not just a potential disruption but a direct challenge to the core business models of UPS and FedEx, which have long relied on contracts with online retailers.

The market reaction suggests investors are factoring in the increased competition. For UPS and FedEx, this necessitates a strategic reassessment of their pricing, service offerings, and long-term growth strategies to counter Amazon's expanding reach.