Internal Boeing messages released this month that showed employees boasting about pressuring regulators into accepting less training for the 737 Max were "unacceptable," CEO David Calhoun told CNBC on Wednesday.

"My stomach turned," he said on CNBC's "Squawk Box," after Boeing reported its first annual loss since 1997, a dismal result from the fallout from last year's 737 Max grounding. "The language is horrible" in those messages.

Boeing released more than 100 pages of internal messages on Jan. 9.

In the communications, provided to the Federal Aviation Administration, lawmakers and the public, employees talked about pushing regulators and airlines — including Lion Air, the carrier whose 737 Max first crashed in October 2018 — to approve the new planes without requiring pilots to undergo simulator training. Other workers raised safety concerns and complained about lax standards.

The messages were from a time period before the two deadly crashes of 737 Max jets, which led global regulators to ground the entire fleet last March after the second crash, which involved an Ethiopian Airlines plane. The two crashes killed a total of 346 people.