Activist investor Third Point's Dan Loeb on Thursday launched a campaign at Honeywell International (HON) seeking to have the company separate its aerospace unit via a spinoff, which the fund said it believes would result in a increase in shareholder value in excess of $20 billion.

The multinational's share price spiked 4% in after-market trading Thursday, rising to $135.01 on the news.

According to the insurgent fund's first quarter investor letter, obtained by TheStreet, Loeb said a move to spin off the aerospace unit would "transform Honeywell into an industrial growth company with a focus on automation and productivity."

In the letter, Loeb said he believes Honeywell trades at a "substantial discount to its industrial peer group." Nevertheless, he said he was "pleased" that recently installed Chief Executive Darius Adamczyk was brought in as the CEO.

Loeb has launched a number of dissident-director battles in the past to help drive his campaigns forward. But Honeywell has some time to consider Loeb's plan. Any director battle the activist fund might want to launch would most likely have to wait until the 2018 annual meeting. For that, Loeb would need to nominate his dissident director candidates between Dec. 25 and Jan. 24.

Honeywell has a $100 million market capitalization.

More from Investing

Immigration, Instagram and Oil - Here's What You Can't Miss Wednesday

Immigration, Instagram and Oil - Here's What You Can't Miss Wednesday

REPLAY: Jim Cramer on Fed Rate Hikes, Oil Prices and Starbucks Worries

REPLAY: Jim Cramer on Fed Rate Hikes, Oil Prices and Starbucks Worries

What Will GM Do With Cruise -- and Is Its Stock Worth $55?

What Will GM Do With Cruise -- and Is Its Stock Worth $55?

3 Must Reads on the Market From TheStreet's Top Columnists

3 Must Reads on the Market From TheStreet's Top Columnists

This Should Be Your Retirement Savings Plan When the Stock Market Crashes

This Should Be Your Retirement Savings Plan When the Stock Market Crashes