As Honeywell’s largest active investor, Elliott Investment Management’s letter to Honeywell International argued that Honeywell should split into two entities—Honeywell Aerospace and Honeywell Automation.

The activist investor, which has amassed a $5 billion stake, is calling for big changes. Honeywell shares were up about 5% on the news.

Activist investor Elliott Investment Management called for a break-up of Honeywell into its aerospace and automation businesses on Tuesday, after saying it had built a stake worth more than $5 billion in the industrial giant.