Diversified conglomerates were long a fixture of the U.S. stock market landscape, with the Dow industrials bolstered by big names such as 3M, General Electric, United Technologies and others. But many of those companies have since broken apart,

Honeywell's stock rallied as much as 7.8% into record territory for the first time in three years, after activist investor Elliott Investment Management disclosed a more than $5 billion stake, but then pulled back.

Activist investor Elliott Investment Management has taken a more than $5 billion stake in Honeywell International and is calling for the conglomerate to split into two separate companies