Amazon and Blue Origin founder Jeff Bezos provides the keynote address at the Air Force Association's Annual Air, Space & Cyber Conference in Oxen Hill, MD, on September 19, 2018. 

“This IS Big News, if you believe in Shipping Elasticity, which we do. The faster you ship, the more people buy. … This could be a key growth catalyst for Amazon for some time,” RBC Capital Markets said.

“We believe the move is consistent with AMZN’s long-standing goal of convenience & selection, but also likely reflects the increasingly competitive retail environment. … We come away with more confidence in Amazon’s ability to stabilize & potentially accelerate revenue growth,” J.P. Morgan said.

Amazon shares traded 1% higher in Friday’s premarket from Thursday’s close of $1,924 a share. Amazon’s earnings after the close topped expectations.

Read what major analysts were saying about one-day Prime delivery: