Boeing's annual free cash flow target of $10 billion may be delayed by about two years to 2027-28 and it would have to raise $30 billion before developing a new aircraft, Wells Fargo said and downgraded the stock.

Boeing slumped on Tuesday after Wells Fargo published a rare bearish take on the stock, saying it's hard to see upside in the shares.

Shares of Boeing fell nearly 8% after Wells Fargo downgraded the company to an underweight rating and cut its price target on the stock. Boeing's stock was on pace for its worst day since January and recently shaved about 90 points off of the Dow Jones Industrial Average.