Mnuchin says use of costly gov't jet was necessary for 'secure communications'

Mnuchin said travel was necessary for national security purposes.

Mnuchin also confirmed that his use of the private jet on Aug. 15 is now under review, as are as at least two other requests for government travel involving the secretary.

“The inspector general is reviewing my travel,” Mnuchin replied. “If there’s suggestions we’ll follow it.”

ABC News' Justin Fishel and Elizabeth McLaughlin contributed to this report.