Tesla stock rallied as much as 5 percent on Monday after CEO Elon Musk made several promises to customers over the weekend. Among other things, Musk promised an Autopilot update by August that will "enable full self-driving features."

He offered the Autopilot detail in response to a customer's criticism:

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Additionally, Tesla's CEO and chairman also teased his 21.9 million Twitter followers with promises of a Roadster "SpaceX option package" to improve acceleration, top speed, braking and cornering and "maybe ... even allow a Tesla to fly."

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While that tweet could easily be mistaken for a jest inspired by "The Jetsons," Musk said it was serious:

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A company spokesperson confirmed that Musk was sincere as well.

Tesla recently held its annual shareholder meeting where executives told investors they had committed to opening a new factory in Shanghai and would become profitable and then cash-flow positive this year.

Many Musk believers take his promises at face value. However, Tesla faces a number of serious challenges and remains among the most shorted stocks on the market.

Tesla recently agreed to settle a class-action lawsuit initiated by Tesla Model S and Model X owners who spent thousands for Autopilot software and extra safety features — like side collision warnings and automated emergency braking — that they said were never delivered.

The company is also facing investigations into whether and how Autopilot may have contributed to crashes involving Tesla vehicles.

Tesla stock closed up by 4.55 percent on Monday afternoon, while the S&P 500 was basically flat. Tesla's stock is still trading down on a year-over-year basis, however. Its shares traded around $359 on this date last year.