Amazon's share price jumped more than 60 percent over the past year, but some stakeholders say the company is in need of better governance measures.

At Amazon's annual shareholder meeting on Wednesday, an activist group called SumOfUs plans to fly a plane overhead with a banner reading, "Bezos Needs a Boss." The gimmick is in support of a proposal calling for Amazon to separate the roles of CEO and chairman.

Jeff Bezos, Amazon's founder and the richest person in the world, holds both positions.

"There is a clear conflict of interest when a corporation's board of directors, which is responsible for overseeing the CEO and representing shareholders, is chaired by that same CEO," Lisa Lindsley, capital markets advisor for SumOfUs, said in a statement.

In a separate letter, SumOfUs wrote that Bezos' dual role at Amazon "weakens" its governance and harms shareholder value. Instead, the company should hire an independent board chair to provide "a balance of power" between the CEO and the board, it said.

"The chairman runs the board," the letter said. "How can the CEO be his own boss?"

An Amazon representative wasn't immediately available for comment.

Bezos' position isn't entirely unusual, particularly in tech. Facebook's Mark Zuckerberg and Salesforce's Marc Benioff are both company founders who also serve as CEO and chairman. But SumOfUs said that separating the roles is "the norm" in Europe, and 51 percent of S&P 500 companies also split those positions.